Providing multiple MSISDN numbers in a mobile device with a single IMSI

ABSTRACT

A SIMM System and method is provided that supports many Mobile Subscriber Integrated Service Digital Network (MSISDN) numbers on a mobile device. The mobile device includes one Subscriber Identity Module (SIM) and one International Mobile Subscriber Identity (IMSI). The SIMM system includes at least one signal gateway that supports the use of numerous MSISDN numbers by the mobile device. The signal gateway couples among components of the public mobile networks to which the MSISDN numbers correspond. The signal gateway connects calls between the mobile device and a first public mobile network using a first MSISDN where, for example, the first public mobile network is in a first country. Likewise, the signal gateway connects calls between the mobile device and a second public mobile network using a second MSISDN where, for example, the second public mobile network is in a second country.

RELATED APPLICATION

This application claims priority from U.S. Patent Application No.60/447,998, filed Feb. 18, 2003.

TECHNICAL FIELD

The disclosed embodiments relate to portable communication networks anddevices.

BACKGROUND

Operators and service providers of mobile and cellular telephoneservices face tremendous challenges in growing their revenue streams inthe face of increasing competition and pricing pressures. Roamingusers/subscribers/devices, referred to as roamers, remain an attractivesource of revenue for operators, and contribute heavily to thebottom-line because of the additional surcharges placed on roaming callsby many operators. In some cases roamers contribute as much as 40% ofthe total revenues, while in most cases roamers contribute approximately8% to 20% of the total revenues. It is thus extremely important to beable to control and influence the roaming network choices that roamershave, in order to maximize the benefits and profits both to the operatoras well as the subscriber.

A particularly attractive segment of the roaming market is users whoroam frequently between two or more networks in two or more countriesand have a need for a local number in each country. A local number ineach country in which a user roams both enables local callers in thevisited country to call the roamers under cheaper local telephone rateswithout worrying about international IDD calls, and presents amulti-national appearance. Such international roamers typically buylocal pre-paid subscriptions to local cellular telephone services invisited countries. Apart from having to change the SIM card in thecellular telephone or handset every time a roamer uses the localcellular services in a visited country, this also results in erosion ofthe operator's roaming revenues in the roamer's home country (homeoperator).

A typical method of supporting two different cellular telephone numbersfor use in different countries has service providers using Dual IMSI SIMcards that contain an IMSI/MSISDN entry for each of the partneringoperators or service providers. When in a first or home calling area,the home IMSI is selected manually or automatically. When in a partnercountry outside of the home country or calling area, the partner IMSI isselected manually or automatically. The dual IMSI approach requires useof a SIM having multiple SMSCs and multiple authentication keys (Ki),among other things, thereby resulting in a number of logisticalproblems. The dual IMSI approach also requires a new type of SIM card,one that includes an STK application. This new SIM card causes the HPMNto extend existing or create new SIM agreements with SIM manufacturers,further increasing costs and complicating the logistics process. Inaddition, each time the location of the device hosting the SIM cardchanges, the STK must determine whether it is in a network that requiresanother home IMSI; this typically results in a significant drain ofbattery power in the host mobile handset.

Consequently, there is a need for operators in one country (home) tojoin forces with operators in another country (visited country) in orderto offer a local MSISDN in the visited country on the same SIM card,thereby creating a monetarily beneficial relationship to both operatorsand the roaming user.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram of a single International Mobile SubscriberIdentity (IMSI) Multiple MSISDN service, under an embodiment.

FIG. 2 is a system block diagram of a single IMSI Multiple MSISDNservice, under an embodiment.

FIG. 3 is a block diagram of a Signal Gateway (SG), under an embodiment.

FIG. 4 is block diagram of the persistent and transit data, under anembodiment.

FIG. 5 is a block diagram of transactional mappings at a Signal Gateway(SG), under an embodiment.

FIG. 6 is a block diagram of a cross-connect deployment topology, underan embodiment.

FIG. 7 is a block diagram of a non-cross-connect deployment topology,under an embodiment.

FIG. 8 is another block diagram of a cross-connect deployment topology,under an embodiment.

FIG. 9 is a block diagram of a Global Title Translation (GTT) routingconfiguration at a Gateway Mobile Switching Center (GMSC) in a HomePublic Mobile Network (HPMN) (GMSC-H), under an embodiment.

FIG. 10 is a block diagram of a Global Title Translation (GTT) routingconfiguration at a Gateway Mobile Switching Center (GMSC) in a ForeignPublic Mobile Network (FPMN) (GMSC-F), under an embodiment.

FIG. 11 is a block diagram of a trunk routing configuration of theGMSC-F.

FIG. 12 is a block diagram of an Integrated Service Digital Network(ISDN) User Part (ISUP) message loopback circuit configuration at a GMSCin a Home Public Mobile Network (HPMN) (GMSC-H), under an embodiment.

FIG. 13 is a block diagram of an interface between a Signal Gateway (SG)and an Intelligent Network (IN), under an embodiment.

FIG. 14 is a block diagram of a system including at least one SignalGateway (SG) and a database, under an embodiment.

FIG. 15 is a block diagram of couplings between Signal Gateways (SGs)and databases in a system, under an embodiment.

FIG. 16 is a block diagram of an ISDN User Part (ISUP) message loopbackcircuit configuration for call fail-over handling, under an embodiment.

FIG. 17 is a block diagram of updated location transaction flowfollowing Signal Gateway (SG) failure, under an embodiment.

FIG. 18 is a block diagram of system redundancy in a system havingSignal Gateways (SGs) coupled to an Ethernet, under an embodiment.

FIG. 19 is a signal flow diagram of a voice call traffic model, under anembodiment.

FIG. 20 is another signal flow diagram of a voice call traffic model,under an embodiment.

FIG. 21 is a block diagram of a system including two Signal Gateways(SGs) and two databases, under an embodiment.

FIG. 22 is a signal flow diagram of an update location transaction,under an embodiment.

FIG. 23 is a signal flow diagram of an update location transaction whenthe SIMM subscriber is in the FPMN, under an embodiment.

FIG. 24 is a signal flow diagram of an update location transactionfollowing failure of a Signal Gateway (SG), under an embodiment.

FIG. 25 is a signal flow diagram of mobile terminated calls when theSingle IMSI Multiple MSISDN (SIMM) subscriber is in a HPMN, under anembodiment.

FIG. 26 is another signal flow diagram of mobile terminated calls whenthe SIMM subscriber is in a HPMN, under an embodiment.

FIG. 27 is a signal flow diagram of mobile terminated calls when theSIMM subscriber is in a HPMN and a Signal Gateway (SG) fails, under anembodiment.

FIG. 28 is another signal flow diagram of mobile terminated calls whenthe SIMM subscriber is in a HPMN and a Signal Gateway (SG) fails, underan embodiment.

FIG. 29 is yet another signal flow diagram of mobile terminated callswhen the SIMM subscriber is in a HPMN and a Signal Gateway (SG) fails,under an embodiment.

FIG. 30 is a signal flow diagram of mobile terminated calls on aMSISDN-H when the SIMM subscriber is in a FPMN, under an embodiment.

FIG. 31 is a signal flow diagram of mobile terminated calls on aMSISDN-F when the SIMM subscriber is in a FPMN, under an embodiment.

FIG. 32 is another signal flow diagram of mobile terminated calls on aMSISDN-F when the SIMM subscriber is in a FPMN, under an embodiment.

FIG. 33 is yet another signal flow diagram of mobile terminated calls ona MSISDN-F when the SIMM briber is in a FPMN, under an embodiment.

FIG. 34 is a signal flow diagram of mobile terminated calls on aMSISDN-F when the SIMM subscriber is in a FP and a Signal Gateway (SG)fails, under an embodiment.

FIG. 35 is another signal flow diagram of mobile terminated calls on aMSISDN-F when the SIMM subscriber is in a FPMN and a Signal Gateway (SG)fails, under an embodiment.

FIG. 36 is yet another signal flow diagram of mobile terminated calls ona MSISDN-F when the SIMM subscriber is in a FPMN and a Signal Gateway(SG) fails, under an embodiment.

FIG. 37 is yet another signal flow diagram of mobile terminated calls ona MSISDN-F when the SIMM subscriber is in a FPMN and a Signal Gateway(SG) fails, under an embodiment.

FIG. 38 is a signal flow diagram of mobile terminated calls on aMSISDN-F when the SIMM subscriber is in a Visited Public Mobile Network(VPMN), under an embodiment.

FIG. 39 is a signal flow diagram of unconditional call forwarding to aSIMM subscriber including calls to an MSISDN-F, under an embodiment.

FIG. 40 is a signal flow diagram of conditional call forwarding to aSIMM subscriber in an FPMN including calls to an MSISDN-H, under anembodiment.

FIG. 41 is another signal flow diagram of conditional call forwarding toa SIMM subscriber in an FPMN including calls to an MSISDN-H, under anembodiment.

FIG. 42 is another signal flow diagram of conditional call forwarding toa SIMM subscriber in an FPMN including calls to an MSISDN-F, under anembodiment.

FIG. 43 is a signal flow diagram of conditional call forwarding to aSIMM subscriber in a VPMN including calls to an MSISDN-F, under anembodiment.

FIG. 44 is a signal flow diagram of call routing when an MSISDN-F iscalled and the subscriber is not in the HPMN, under an embodiment.

FIG. 45 is another signal flow diagram of call routing when an MSISDN-Fis called and the subscriber is not in the HPMN, under an embodiment.

FIG. 46 is a signal flow diagram of call routing when an HPMN user(local or roamer) calls an MSISDN-F of a SIMM subscriber and thesubscriber is not in the FPMN, under an embodiment.

FIG. 47 is another signal flow diagram of call routing when an HPMN user(local or roamer) calls an MSISDN-F of a SIMM subscriber and thesubscriber is not in the FPMN, under an embodiment.

FIG. 48 is yet another signal flow diagram of call routing when an HPMNuser (local or roamer) calls an MSISDN-F of a SIMM subscriber and thesubscriber is not in the FPMN, under an embodiment.

FIG. 49 is still another signal flow diagram of call routing when anHPMN user (local or roamer) calls an MSISDN-F of a SIMM subscriber andthe subscriber is not in the FPMN, under an embodiment.

FIG. 50 is a signal flow diagram for a mobile terminated Short MessageService (SMS) message to an MSISDN-H when the subscriber is in an FPMN,under an embodiment.

FIG. 51 is a signal flow diagram for a mobile terminated SMS message toan MSISDN-H when the subscriber is in an FPMN and the targeted SignalGateway (SG) fails, under an embodiment.

FIG. 52 is another signal flow diagram for a mobile terminated SMSmessage to an MSISDN-H when the subscriber is in an FPMN and thetargeted Signal Gateway (SG) fails, under an embodiment.

FIG. 53 is a signal flow diagram for a mobile terminated SMS message toan MSISDN-F when the subscriber is in an FPMN, under an embodiment.

FIG. 54 is another signal flow diagram for a mobile terminated SMSmessage to an MSISDN-F when the subscriber is in an FPMN, under anembodiment.

FIG. 55 is a signal flow diagram for a mobile terminated SMS message toan MSISDN-F when the subscriber is in an VPMN, under an embodiment.

FIG. 56 is a signal flow diagram for a mobile originated SMS message,under an embodiment.

FIG. 57 is a signal flow diagram for SMS message re-delivery management,under an embodiment.

FIG. 58 is another signal flow diagram for SMS message re-deliverymanagement, under an embodiment.

FIG. 59 is a signal flow diagram for multiple HPMN support, under anembodiment.

FIG. 60 is a signal flow diagram for Signal Gateway (SG) recovery, underan embodiment.

FIG. 61 is a signal flow diagram for use of a Signal Gateway (SG) withGeneral Packet Radio Service, under an embodiment.

FIG. 62 is another signal flow diagram for use of a Signal Gateway (SG)with General Packet Radio Service, under an embodiment.

FIG. 63 is yet another signal flow diagram for use of a Signal Gateway(SG) with a General Packet Radio Service (GPRS), under an embodiment.

FIG. 64 is a signal flow diagram for use of a Signal Gateway (SG) in thetransfer of Message Application Part (MAP) messages onSend-Authentication, Unstructured Supplementary Service Data (USSD) andsupplementary MAP services, under an embodiment.

FIG. 65 is another signal flow diagram for use of a Signal Gateway (SG)in the transfer of Message Application Part (MAP) messages onSend-Authentication, Unstructured Supplementary Service Data (USSD) andsupplementary MAP services, under an embodiment.

FIG. 66 is yet another signal flow diagram for use of a Signal Gateway(SG) in the transfer of Message Application Part (MAP) messages onSend-Authentication, Unstructured Supplementary Service Data (USSD) andsupplementary MAP services, under an embodiment.

FIG. 67 is another signal flow diagram for use of a Signal Gateway (SG)with Multimedia Messaging Service, under an embodiment.

ACRONYMS

Following are a list of acronyms used herein.

-   International Mobile Subscriber Identity (of HPMN) (IMSI);-   Mobile Subscriber ISDN Number (phone number) (MSISDN);-   Single IMSI Multiple MSISDN Service (SIMM);-   Subscriber Identity Module (SIM);-   Home Public Mobile Network who intends to provide MSISDN Service    (HPMN);-   Foreign Public Mobile Network who intends to partner with HPMN for    Multiple MSISDN Service (FPMN);-   Mobile Switching Center (MSC);-   Signal Gateway (SG) or Signal Gateway (SG);-   Gateway MSC (GMSC);-   GMSC in HPMN (GMSC-H);-   GMSC in FPMN (GMSC-F);-   GMSC in VPMN (GMSC-V);-   MSISDN of the Multiple MSISDN Service allocated by HPMN in HPMN    numbering plan (MSISDN-H);-   MSISDN of the Multiple MSISDN Service subscriber in the FPMN    (Co-operating VPMN) numbering plan (MSISDN-F);-   Signaling System 7 (SS7);-   Visited Mobile Switching Center (VMSC);-   Serving VMSC in HPMN (VMSC-H);-   Serving VMSC in FPMN (VMSC-F);-   Serving VMSC in VPMN (VPMN is not HPMN/FPMN) (VMSC-V);-   Associated Public Mobile Network for SMS Inter-working (APMN);-   Call Detail Record (CDR);-   Call Forwarding in Busy (CFB);-   Call Forwarding on Not Reachable (CFNR);-   Call Forwarding on No Reply (CFNRy);-   Call Forwarding Unconditional (CFU);-   Circuit Switch Data (CSD);-   Digital Distribution Frame (DDF);-   Forwarded-To-Number typically used in Call Forwarding (FTN);-   General Packet Radio Service (GPRS);-   Gateway GPRS Service Node (GGSN);-   GPRS Roaming Exchange (GRX);-   Serving GPRS Service Node (SGSN);-   Global Title (SS7 parlance) (GT);-   Home Location Register (HLR);-   Intelligent Network (IN);-   Intelligent Network Application Part (INAP);-   Inter Operator SMS within HPMN (IOSMS);-   International Roaming Expert Group (IREG);-   ISDN User Part message from SS7 stack (ISUP);-   Interactive Voice Response (IVR);-   Late Call Forwarding (LCF);-   Message Application Part (from GSM 09.02 GSM Standards) (MAP);-   Mobile Global Title (derived from IMSI) (MGT);-   Mobile Station Roaming Number (MSRN);-   Originally Called Number (OCN) (same as ODN);-   Originally Dialed Number (ODN) (same as OCN);-   Outreach Messaging (Enhanced version of legacy SMS Welcome) (OM);-   Optimized Routing (OR);-   Packet Data Protocol (PDP);-   Provide Roaming Number MAP message (PRN);-   Service Control Point (SCP);-   Signal Control Connection Part (SCCP);-   Send Routing Information MAP message (SRI);-   Short Message Service (SMS);-   Short Message Service Center (SMSC);-   SMSC in HPMN (SMSC-H);-   SMSC in APMN (where APMN is not HPMN or FPMN) (SMSC-A);-   SMSC in FPMN (SMSC-F);-   Transfer Accounting Procedure (TAP);-   Transfer Accounting Data Interchange Group (TADIG);-   Transaction Capability Part (TCAP);-   Translation Type (SS7 parlance) (TT);-   Virtual Home Environment (VHE);-   Visited Location Register (VLR);-   Serving VLR in HPMN (VLR-H);-   Serving VLR in FPMN (VLR-F);-   Serving VLR in VPMN (VPMN is not HPMN/FPMN) (VLR-V);-   Visited Public Mobile Network (other than HPMN or FPMN) (VPMN);-   Wireless Fidelity (WiFi);-   Basic Call State Model (BCSM);-   Customized Applications for Mobile network Enhanced Logic (CAMEL);-   Camel related message from SCF to SSF (Connect, Continue);-   Detection Point (DP);-   Deflected To Number (DTN);-   Dialed Services CAMEL Subscription Information (D-CSI);-   Event Detection Point (EDP);-   Gateway MLC (GMLC);-   GPRS Service Switching Function (gprsSSF);-   GPRS CAMEL Subscription Information (GPRS-CSI);-   GSM Service Control Function (gsmSCF);-   GSM Specialised Resource Function (gsmSRF);-   GSM Service Switching Function (gsmSSF);-   Home PLMN (HPLMN);-   InitialDP (IDP);-   Information Element (IE);-   Information Flow (IF);-   Intelligent Peripheral (IP);-   Interrogating PLMN (IPLMN);-   IP Multimedia Subsystem Service Control Interface (ISC);-   Location Services (LCS);-   Localised Service Area (LSA);-   Mobility Management event Notification CAMEL Subscription    Information (M-CSI);-   Mobile Forwarding (MF);-   Mobile Location Center (MLC);-   Mobile Originating (MO);-   Mobile Terminating in GMSC (MT);-   Network CAMEL Service Information (N-CSI);-   North American (NA);-   Network Node Interface (NNI);-   Originating Basic Call State Model (O-BCSM);-   Originating CAMEL Subscription Information (O-CSI);-   Operator Determined Barring (ODB);-   Operator Specific Service (OSS);-   Packet Data Protocol (PDP);-   Point In Call (PIC);-   Public Land Mobile Network (PLMN);-   Serving GPRS Support Node (SGSN);-   Service Logic Program Instance (SLPI);-   Service Management Function (SMF);-   Serving MLC (SMLC);-   Short Message Service CAMEL Subscription Information (SMS-CSI);-   Supplementary Service Notification CAMEL Subscription Information    (SS-CSI);-   Terminating Basic Call State Model (T-BCSM);-   Terminating CAMEL Subscription Information (in the GMSC) (T-CSI);-   Trigger Detection Point (TDP);-   Transfer Protocol Data Unit (TPDU);-   Translation Information Flag (TIF-CSI);-   USSD CAMEL Subscription Information (U-CSI);-   USSD General CAMEL Service Information (UG-CSI);-   User Network Interface (UNI);-   Visited PLMN (VPLMN);-   Mobile Terminating in VMSC (VT);-   VMSC Terminating CAMEL Subscription Information (VT-CSI);-   Charging data collection interface between a CDR transmitting unit    (e.g. an SGSN or a GGSN) and a CDR receiving functionality (a CGF)    (Ga);-   Interface between an SGSN and a BSS (Gb);-   Interface between a GGSN and an HLR (Gc);-   Interface between an SMS-GMSC and an SGSN, and between an SMS-IWMSC    and an SGSN (Gd);-   Interface between an SGSN and an EIR (Gf);-   Reference point between GPRS and a packet data network (Gi);-   Interface between two GSNs within the same PLMN (Gn);-   Interface between two GSNs in different PLMNs (Gp) (the Gp interface    allows support of GPRS network services across areas served by the    co-operating GPRS PLMNs);-   Interface between an SGSN and an HLR (Gr);-   Interface between an SGSN and an MSC/VLR (Gs);-   Interface between the RNS and the core network (Iu) (also considered    as a reference point);-   Kilobits per second (kbit/s);-   Megabits per second (Mbit/s) (1 Mbit/s=1 million bits per second);-   Reference point between a non-ISDN compatible TE and MT (typically    this reference point supports a standard serial interface) (R);-   The service area for which the location of an MS is reported    (Reporting Area);-   The location accuracy level needed for service management purposes    in the 3G-SGSN, e.g. a routing area or a cell (the 3G-SGSN can    request the SRNC to report: i) the MS's current service area; ii)    when the MS moves into a given service area; or iii) when the MS    moves out of a given service area) (Service Area);-   Interface between the mobile station (MS) and the A/Gb mode network.    The Um interface is the MS to network interface for providing GPRS    services over the radio to the MS (Um); and-   Interface between the mobile station (MS) and the Iu mode network.    The Uu interface is the Iu mode network interface for providing GPRS    services over the radio to the MS (Uu).

DETAILED DESCRIPTION

A Single IMSI Multiple MSISDN (SIMM) System and Service is provided thatsupports providing mobile communication devices with multiple MobileSubscriber ISND Numbers (MSISDN) using one International MobileSubscriber Identity (IMSI). The SIMM System/Service does not require anew type of SIM card in a mobile device or handset. The SIMMSystem/Service allows operators in one country (home) to join forceswith operators in another country (visited country) in order to offer alocal MSISDN in the visited country on the same SIM card, therebycreating a monetarily beneficial relationship to both operators and theroaming user. The SIM for use under the SIMM System/Service includes asingle IMSI (and the associated parameters, e.g., Ki) from the HPMN; theSIM does not have the FPMN MSISDN. The subscriber is allocated a FPMNMSISDN in addition to the HPMN MSISDN. The subscriber registers with theHPMN IMSI. This simplifies the user experience as the user need not beconcerned with whether they are in the local country or are roaming whenregistered with the FPMN network. The SIMM System/Service describedbelow does not require an intelligent SIM application to automaticallydetect the FPMN network, resulting in reduced power usage. It also makesit simple for subscribers to use home services despite having a localnumber. This makes it easier to transparently support GPRS and USSDservices.

The following description provides specific details for a thoroughunderstanding of, and enabling description for, embodiments of the SIMMSystem/Service. However, one skilled in the art will understand that theSIMM System/Service may be practiced without these details. In otherinstances, well-known structures and functions have not been shown ordescribed in detail to avoid unnecessarily obscuring the description ofthe embodiments of the SIMM System/Service. The headings provided hereinare for convenience only and do not affect the scope or meaning of theclaimed invention.

The mobile devices described herein include, for example, cellulartelephones, personal computers, portable computing devices, portabletelephones, portable communication devices, subscriber devices or units,and personal digital assistants. The mobile devices, which also may bereferred to as “mobile communication devices,” “portable communicationdevices” and “communication devices,” can include all such devices andequivalents, and are not limited to communication devices that arewireless. The communication networks described herein support thetransfer of information including voice and data signals between themobile devices and the operator or service provider systems via at leastone of wireless couplings, wired couplings, and a combination ofwireless/wired couplings using one or more communication protocols knownin the art. The networks described herein can use at least one of GlobalSystem for Mobile Communications (GSM), General Packet Radio Service(GPRS), Code Division Multiple Access (CDMA), and Time Division MultipleAccess (TDMA) communication protocols, for example, but are not solimited.

The SIMM System/Service for roaming is a subscription-based serviceprovided by a service provider, also referred to as an operator, but isnot so limited. The SIMM service provides a local number at each partnernetwork for a subscriber, also referred to as a user. The local numbercan be assigned to a subscriber permanently or temporarily dependingupon operator requirements. The SIMM service for roaming is normallyapplied by an HPMN operator for (international and national) outboundroamers at a partner FPMN involving some logistical arrangements at theFPMNs. The SIMM service for roaming can also be applied to (national orinternational) inbound roamers without involving any HPMN logistics. Inparticular, it can be deployed for a Mobile Virtual Network Operator(MVNO).

FIG. 1 is a block diagram of a Single IMSI Multiple MSISDN (SIMM)service, under an embodiment. The SIMM service uses at least one SignalGateway (SG) to support international roaming for outbound roamershaving permanent local numbers as well as providing temporary localnumbers, national roaming and inbound roaming (nationally orinternationally). The Signal Gateway (SG) is also referred to as aSignaling Gateway (SG). The SIMM solution is built on a Signal RelayGateway Framework (SRGF) which also supports Multiple IMSI MultipleMSISDN (MIMM) and Multiple IMSI Single MSISDN (MISM) within the sameoperator or between different operators (across different countries) andwithin a single SIM or multiple SIMs, but is not so limited.

The Signal Gateway Relay Framework (SGRF) of an embodiment is forworldwide deployment by cellular telephone operators or serviceproviders. The different applications on the SGRF share many fundamentalfeatures although they apply different logics and procedures. The SGRFof an embodiment stores SIMM service subscription information androaming information of SIMM subscribers at the FPMN. The SGRF alsoextends across GSM and CDMA technologies. The SGRF platform has thecapability to impersonate various GSM network entities in order toprovide many additional services. The platform of an embodiment is apure SS7-based solution that functions as virtual HLR, virtual VLR,virtual GMSC, virtual VMSC, virtual SMSC and virtual service nodedepending on interactions with various SS7 network elements. The SGRF isvirtual in the sense that it does not store subscription data as in HLR,does not have switching support as in GMSC, and does not have triggermechanisms, etc.

As described above, cellular telephone operators face tremendouschallenges in growing their revenue streams, in the face of increasingcompetition and pricing pressures. Roamers remain an attractive sourceof revenue or operators, and contribute heavily to revenues.

The SIMM System/Service targets users who roam frequently between twocountries and have a need for a local number in each network, either toenable local users to call them at a cheap rate without worrying aboutinternational IDD calls or to present a multi-national appearance.Consequently, the SIMM System/Service allows the operators to be able tocontrol and influence the roaming network choices that roamers have, inorder to maximize the benefits and profits both to the operator as wellas the subscriber. In so doing, operators in one country (home) can joinforces with operators in another country (visited country) in order tooffer a local MSISDN in the visited country on a singe SIM card, therebycreating a monetarily beneficial relationship.

The operators in different counties can offer local MSISDN via a singleSIM card under multiple approaches. A first approach requires the twooperators to cooperate in the building of a dual IMSI SIM card whichautomatically detects the country the user is in and uses the IMSI ofthat country (Multiple IMSI with Multiple MSISDN, or Multiple IMSI withSingle MSISDN-H). A second approach requires the two operators tocooperate and map the HPMN MSISDN on the network side to a local MSISDNin the partner foreign network.

The SGRF of an embodiment supports both approaches by functioning as avirtual HLR for the subscribers. Under the first approach the SGRF willhost for the FPMN IMSI and MSISDN allocated to the HPMN and use HPMN Aucfor authenticating subscribers. In this way, the Multi-IMSI SIM onlyneed to have the HPMN keys and algorithms, eliminating the logisticalcomplexity of security management. This first approach also makes iteasier for billing as a local subscriber at FPMN since there is a localIMSI involved. However USSD service which is IMSI-based, will alwayshave to go through the SGRF, making it less transparent. For GPRS whichis also IMSI-based, if the FPMN IMSI is chosen as the home IMSI, thiscould introduce problems to APN (unless it has the absolute networkoperator path) and PDP contexts (unless GGSN grants permission to theFPMN IMSI) set up. In the rare event of failure of the SGRF, subscribersunder the first approach will not however be able to register at FPMN asa local subscriber.

To avoid confusion in billing at a third party operator, both the SGRFand the SIM application will need to disable and reject FPMN IMSI atVPMN. In this case, the SIM application will need to switch back to HPMNIMSI. This might cause some confusion to the user since the SIMapplication will not be able to distinguish a loss of coverage in FPMNor need to swap in another home IMSI for registration unless there is aregistration of a network. When the subscriber registers (e.g. briefly)as a roamer at a home network (non HPMN home operators can be rejected)when the home IMSI in the SIM has the value of the FPMN IMSI, this couldintroduce further confusion. It is possible to control the STKapplication from the HPMN network side for which home IMSI to use, butthis would further complicate the logistics and add costs (e.g. SMS).

Furthermore, under the first approach, the service will use a new typeof SIM that includes an STK application. This could require HPMN toextend existing or create new SIM agreements with SIM manufacturers,further adding costs and complicating the logistics process. Whenmultiple IMSI is introduced or extended, the HPMN will need to updatethe local IMSI list in the SIM (either via OTA or change of SIM), whichagain adds logistic complexity. In addition, each time a new locationchanges, the STK will need to perform a check to see if it is in anetwork that requires another home IMSI. This could drain battery powersignificantly.

On the billing side, under the first approach, when registering with theFPMN IMSI at a FPMN network (e.g., Beijing Mobile), the network will seethe subscriber as a domestic subscriber (e.g., from Guang Dong Mobile)which it would bill in a standard way. If this is desired, then there isno problem. However if the FPMN still wants to view this subscriber as aroamer while applying centralized discounts (e.g., by CMCC in ChinaMobile), then this would present a problem, as the local networks willsettle among themselves rather than going through the central body. Thisproblem usually does not arise in small networks or small countries.

Turning to the second approach, the SGRF of an embodiment hosts the FPMNMSISDN allocated to HPMN. The subscriber therefore always registers withHPMN IMSI. This simplifies the user experience as the user need not beconcerned with whether they are regarded as a roamer or a localsubscriber when registered with the FPMN network. This approach does notrequire an intelligent SIM application to automatically detect the FPMNnetwork, thereby reducing device battery consumption and reducing costs.This second approach also simplifies the use by subscribers of homeservices despite having a local number. However since the subscriber'sIMSI is still a HPMN IMSI, while it helps HPMN in gaining more roamingrevenue, it will require slightly more complex billing solution than thefirst approach if FPMN and HPMN want to place subscriber calls on parwith local calls rather than roaming calls when roaming in FPMN.Nevertheless, it is easier under the second approach to transparentlyfall back as a normal roamer in the rare situation where the SGRF fails.

Therefore, service under the second approach generally involves fewerlogistical challenges when compared to service under the first approach.Service under the second approach also allows the home operator to offera service whereby the frequent roamer can get MSISDN in more than onecountry without a requirement for a new SIM or OTA process to change theSIM values. The roamer is always an HPMN subscriber which means thatcalls (including international and roaming calls) made by the subscribercontribute revenue towards the home operator regardless of thesubscriber's location.

1. Service Description

The SIMM service is offered in collaboration with a participatingoperator in a foreign country (referred to as the FPMN). Consequently,the HPMN of an embodiment has bilateral roaming agreements with the FPMNoperator for Voice and SMS services.

The target market for the SIMM service is subscribers who frequentlyroam between HPMN and FPMN and who have a need for local numbers in bothnetworks. Traditionally, these roamers buy pre-paid subscriptions inFPMN and use that number to make outgoing calls. However, if the roamershave a single phone and have swapped out the HPMN SIM card, they willnot be able to receive MN calls and SMS messages. Also, when the roamersare back in HPMN, they may not be able to receive calls on their FPMnumber.

The SIMM service of an embodiment solves this problem by allowingsubscribers or users to receive calls on both numbers (HPMN and FPMN)without swapping the SIM card. Subscribers also receive SMS messagesaddressed to both numbers.

Users do not have to do anything special in order to use the SIMMservice other than getting a new SIM card. They can retain their HPMNnumbers but will get a new FPMN number. It is possible for the HPMN toenter into agreements with multiple FPMNs in various countries and offera “set of numbers” on a single IMSI. There are no additional changes forthe subscribers once they receive a new SIM card. Hence, subscribers canchoose to add local MSISDN numbers for countries that they visit mostfrequently.

In a country where Mobile Number Portability (MNP) is supported, it ispossible for the service provider or operator to acquire subscribersfrom other operators and offer them the SIMM service. It is alsopossible for subscribers to port-out the existing HPMN numbers; howeverthey cannot port out the FPMN number. As a result, the SIMM serviceprovides a lock-in of services with the HPMN.

The SIMM service does not impact the subscriber's GPRS, USSD and SMSservices. It is just transparent as a normal subscriber for most casesof these services. The MMS, IN, Camel, and 3G services should notinvolve the SGRF and so should not be impacted from a normal subscriberperspective.

The SIMM Service charges can be combined with regular charges or shownas separate charges for the service. The particular presentation optionis left to the operator.

The SIMM service can also be used for privacy management. The subscribercan choose to route calls from one number directly to voicemail, forexample, while letting calls on other numbers ring through to the mobiledevice. The subscriber chooses call routing via preference setting usingUSSD or MO-SMS, but is not so limited.

The SIMM service can also be used for subscribers who do not want toreceive rerouted calls when roaming, but rather want the calling partyto pay for the international portion of the call by asking the caller tocall using the FPMN number. In this way, when the calling party callsthe HPMN number, the call will be immediately forwarded to a voicemailthat says, for example, “I am in China, to reach me you must call myChina number which is 123456789”.

1.1. Comparison with Additional Numbers by HLR

Some HLR vendors offer a modification of an additional number feature tomimic SIMM service because, in the HLR approach, the subscriber can havemultiple MSISDNs. Depending on the registered network, HLR can selectthe right MSISDN to send to the VLR. However, this approach involvesmodifications of the existing HLR and can introduce serious problemswhen the HLR is upgraded. The SIMM System/Service provided herein hasnumerous advantages when compared to the HLR approach, including thefollowing: supports CDR thru at least one of ISUP loopback, IN, and mapinterface; controls optimal routing; controls trunk routing over speciallines to reduce rerouted costs; offers special dial service numbers(e.g., customer care number) and routes these calls; allows HPMN tocontrol whether a subscriber can roam to non-FPMN networks in an FPMNcountry; performs optimal routing for late call forwarding when thesubscriber is in an FPMN network; controls SMS relay to guarantee SMSdelivery on MSISDN-F for outbound roamers; allows subscribers to changeCLI on demand via USSD; allows subscribers to disable MSISDN-H/Frerouting on demand via USSD; and allows subscribers to disableMSISDN-H/F international rerouting but allows local rerouting (e.g.,calls on MSISDN-F when the subscriber is in FPMN country) on demand viaUSSD.

2. Technology and Implementation Architecture

The SIMM System/Service of an embodiment relies logically on thepresence of a Signal Gateway function, also referred to herein as aSignal Gateway function or Signal Gateway (SG). The Signal Gatewayfunction is a combination of an SCCP node and a Service Node, but is notso limited.

2.1. Physical Location of the Signal Gateway

The physical location of the Signal Gateway can be at HPMN or FPMN basedon operator requirements. For those partners that do not host the SignalGateway, routing configurations will send ISUP calls over dedicatedleased lines and to direct MAP and TCAP signaling to the Signal Gatewayacross countries. For the purpose of the description herein, the SignalGateway is assumed to be hosted at the HPMN, but is not so limited. Thesignaling and architecture associated with the Signal Gateway is similarregardless of the location of the Signal Gateway.

2.2. Basic Network Architecture

FIG. 2 is a system block diagram of a Single IMSI Multiple MSISDN (SIMM)system, under an embodiment. Note that the Signal Gateway function isonly at the HPMN and need not be installed at FPMN or any other VPMN.Hence, it imposes minimum operations load on an FPMN.

The SIMM System supports many Mobile Subscriber Integrated ServiceDigital Network (MSISDN) numbers on a mobile device. The mobile deviceincludes one Subscriber Identity Module (SIM) and one InternationalMobile Subscriber Identity (IMSI). The SIMM system includes at least onesignal gateway that supports the use of numerous MSISDN numbers by themobile device. The signal gateway couples among components of the publicmobile networks to which the MSISDN numbers correspond. The signalgateway connects calls between the mobile device and a first publicmobile network using a first MSISDN where, for example, the first publicmobile network is in a first country. Likewise, the signal gatewayconnects calls between the mobile device and a second public mobilenetwork using a second MSISDN where, for example, the second publicmobile network is in a second country.

A Signal Gateway function couples to the GMSC-H for Signaling with Voiceloop-back at the GMSC-H. The GMSC-H is also coupled to the FPMN througha leased line that is provided by an ISC, but is not so limited. Thisleased line is used to carry SS7 signaling as well as voice traffic forMultiple MSISDN subscribers. The Signal Gateway is also responsible forgenerating Call Detail Records that are used to enable special billingof calls and SMS for the Multiple MSISDN subscribers.

Due to the SS7 version differences on the leased line, HPMN arrangeswith a vendor and/or an ISC to provide a SS7 converter. A leased linewill be used to route calls and their associated ISUP signaling thatwill involve call path between FPMN and HPMN. The leased line alsoprovides the signaling path for SCCP routing on any MSISDN-F globaltitle.

2.3. Signal Gateway Internal Architecture

The Signal Gateway function of an embodiment includes at least oneSignal Gateway. FIG. 3 is a block diagram of a Signal Gateway (SG),under an embodiment. Each Signal Gateway can be implemented on a SunSolaris platform, for example, but is not so limited. It can host up tofour DataKinetics Septel Boards with each having four E1 interfaces.Each board processes SS7 messages up to MTP 2/3. Higher level messagesare distributed to 2 pools of User Part Application Instances. One pool(called MAP server) is for processing SCCP messages. The other (calledISUP server) is for processing ISUP loopback messages.

There is a watchdog process which oversees the state of each appinstances. Whenever an app instance is stopped for some reason, thewatch dog kills the instance and starts a new one. If all instances of aparticular application protocol stopped for some reason, the watch dogkills the SS7 stack on each DK first before it kills all instances ofany application protocol. It will then restart the application instancesof all application protocols followed by starting the SS7 stack on eachDK card.

There are many types of persistent information in the memory. The memoryalso contains many types of temporary information.

The Signal Gateway also has SNMP agent and MIB. It also allows SCCP GTTconfiguration and MTP3 routing table. The OA&MP interface is a webinterface to allow operators to provision new customers and othermaintenance functions.

2.3.1. Persistent and Transit Data

FIG. 4 is block diagram of the persistent and transit data, under anembodiment. There are many types of persistent data which are maintainedin the memory before they are written to an Oracle DB. Forhigh-availability, redundancy support and best performance, the OracleDB best resides in a separate physical box.

The memory data also acts as a cache for the database. The databaseserver also has another level of cache which hosts a copy of the memorydata in the Signal Gateway ion and acts like a shared memory to theSignal Gateways.

The Subscriber Data is provisioned by the operator via a web interfaceor stored procedures. It contains the HPMN MSISDN-H number, IMSI, anyFPMN MSISDN-F number. It also contains several flags. The MSISDN-F #forward call flag is to enable/disable of call-re-routing when thesubscriber is called on MSISDN-F but not registered in FPMN network. TheMSISDN-F # CF flag is to enable/disable of call-re-routing to any callforwarding value (e.g. voicemail) when the subscriber is called onMSISDN-F but not registered in FPMN network and not reachable forwhatever reason (e.g. ECF or CFU or LCF). The idea is to set redirectioncounter=6 (or set call diversion indicator CDI=0) in the IAM message todisallow call-forwarding. The MSISDN-F # forward default number flag isto enable/disable of call-re-routing to an operator controlled defaultnumber (e.g. FPMN announcement or customer care) when the subscriber iscalled on MSISDN-F but not registered in FPMN network. In all 3 cases,the objective is to provide the flexibility to SIMM subscribers to avoidpaying IDD call-rerouting. Also in all 3 cases, CFU for MSISDN-F will bedisabled when any of the 3 flags is set.

The FTN-no-change flag allows a subscriber to have the option todirectly route the late call forwarding call to the FTN without beingreplaced by a virtual FTN to cause the call routed through the SignalGateway.

Sometimes, an operator has its own service node platform that need beintegrated with the Signal Gateway. CSL is such an operator. The RCM(Roaming Call Management) flag indicates whether the ISUP loopback callshould go through the CSL service node platform. If it is set, theSignal Gateway will produce a special prefixed number so that the GMSC-Hwill route the call the CSL service node and it sets the generic numberfield to MSISDN-H where the number qualifier indicator is set toaddition called number in the IAM message. The service node can offer HKringback tone service to SIMM subscribers.

There is also an operator-level controlled CF default number, e.g. avirtual voicemail number. If the RCM flag is set, all condition FTN willbe replaced by this default number for routing from VMS C-F to theSignal Gateway. The Signal Gateway can then replace the virtual numberto a real number (e.g. voicemail number such as 19-MSISDN-H where 19 isCSL's internal routing number for voicemail).

There may be other flags related to RCM service which is a CSL specificservice where customization will be done at implementation stage.

The roamer information for a subscriber is created when the SIMMsubscriber successfully registers with a FP network. It contains theVMSC, VLR and other information (e.g. forwarding values) that arecollected from both VLR during updateLocation and HLR (e.g. Camel andGPRS info) during insertSubscriberData. In particular, it contains theassignment of a FTN-F pool # to each conditionally forwarded FTN value.The roamer information data is initially maintained in the memory and/ordisk before it is sent to the Oracle DB only after a successfulregistration.

The roamer information will be removed upon receiving a cancellationfrom HLR. However before this is carried out, a copy is sent to theroamer information history DB. This is used to examine SIMM subscriberroaming behavior etc for reporting purpose.

The Optimal Routing DB contains the network information on whether callson MSISDN-F number ranges can be optimally routed based on theinterrogating MSC/GMSC address, the destination VMSC address. Thisinformation is maintained by the HPMN operator via a web interface orstored procedures.

The Call Context DB maintains the current ISUP loopback call (includingforwarding) context of a SIMM subscriber. The context is maintained inthe memory and is cleared as soon as a call is released/aborted. Thereis also a flag when set to indicate the current call context has beenestablished or forwarded. This flag is used to control whether a secondcall to a subscriber registered in FPMN network will go straight intoforwarding mode or not. There are no simultaneous call contexts for asubscriber registered at FPMN.

The HPMN # pool contains the pool of dedicated HPMN numbers used by theSignal gateway function to ensure GMSC-H will loopback the call throughthe Signal Gateway when the subscriber is registered in FPMN but calledby the MSISDN-H number. It also contains the mapping of a dedicated HPMNnumber to the current assigned MSRN-F number obtained by the SignalGateway from VLR-F to establish the call. The GMSC-H will set up thecall to MSRN-F over the leased line through GMSC-F.

The FPMN # pool contains the pool of dedicated FPMN numbers assigned bythe Signal gateway function to ensure the call from the FPMN will berouted over the leased line to GMSC-H which then loops-back the callthrough the Signal Gateway when the subscriber is called by the MSISDN-Fnumber. It also contains the mapping of a dedicated FPMN number to thecurrent assigned MSRN number obtained by the Signal Gateway fromHLR/VLR-F to establish the call.

The FPMN FTN # pool contains the pool of dedicated FPMN numbers assignedby the Signal gateway function for a conditionally forwarding value fora SIMM subscriber in the FPMN to ensure the late forwarded call will berouted over the leased line to GMSC-H which then loops-back the callthrough the Signal Gateway when the subscriber is registered in FPMN andcalled by the MSISDN-F/MSISDN-H number.

The FPMN# pool and the FTN # pool can share the same dedicated FPMNnumbers. The FTN number pool can be eliminated if FPMN supports OCNcapability.

The CDR contains the call detailed records for all the ISUP calls thathave been looped through a Signal Gateway. Other than the standardparameters, a CDR record will contain which VMSC/GMSC the calloriginated from, which destination VMSC/VLR/MSRN of the call, what pooltype and number has been used for the set up of the call.

FIG. 5 is a block diagram of transactional mappings at a Signal Gateway(SG), under an embodiment. The transaction mapping contains the mappingof the TCAP transactional dialog of the Signal Gateway function with thecalling GT on one side and the TCAP transactional dialog of the SignalGateway function with the called GT on the other side. The SignalGateway function can distinguish transactions initiated by the callingGT using the calling GT and its associated originating transactionidentifier. However this transaction cannot be relayed to the called GTside since the Signal Gateway function (with a single GT that does notcorrespond to any calling GT) cannot determine the correspondingoriginal calling GT from the response from the called GT to relay backthe response. The Signal Gateway will need to create a new uniquetransaction with the called side and relates this transaction with thetransaction generated from the calling side. Note that the transactionidentification (ID) (destination or origination) need only be unique forthe Signal Gateway function.

However if there is a unique SG GT for each calling GT from theinitiating operation of transaction, the transaction can then be relayedacross the called side. Therefore the transaction ID mapping must beunderstood as a logical mapping. Depending on the actual implementationchoice, the physical mapping might involve the same transaction ID(since the calling GT could be made unique with a unique SG GT thatcorresponds to the initiating entity of the operation of a transaction).

To simplify the description, a logical SG GT is used uniformly in thecall flows to represent a Signal Gateway global title. The actualphysical SG GT used varies according to the implementation choices. Whenusing a unique physical SG GT to correspond to each network element(e.g. HLR, VLR, VMSC etc) the correct notation should beSG-network-element.

2.3.2. Deployment Topology

The Signal Gateway function in HPMN is implemented in two physicalSignal Gateways. Each is connected to a GMSC-H using SS7 links for bothSS7 as well as ISUP signaling. In an embodiment, ISUP loop-backSignaling (only ISUP signals are sent to the Signal Gateway while voicetrunks are looped back at the GMSC-H) handles ISUP calls for billing andcall control. This enables voice trunks to not get hauled all the way tothe Signal Gateway but uses the spare port capacity already provisionedon the switch.

FIG. 6 is a block diagram of a cross-connect deployment topology, underan embodiment. Each Gateway is assigned two Signal Point Codes. One SPC(SPC0) is common across both gateways and the other SPC is unique toitself (SPC1 and SPC2). Each gateway is also assigned a distinguishingGlobal Title, GT1 and GT2 respectively.

The Signal gateways will be connected to 2 GMSCs of HPMN in across-connect manner. However due to the cost of ISUP loopback circuits,one GMSC may also be used. Each GMSC will have two links to each SignalGateway. There are six different linksets created. A linkset containslinks that share the adjacent signal point code. Since the two SignalGateways also have a common SPC (SPC0), the GMSC1-SPC0 can have afour-link linkset across two Signal Gateways, resulting greaterfail-over support. Each GMSC will also have a two-link linkset with eachSignal Gateway's unique SPC (SPC1, SPC2) respectively. Note that a linkcan participate in more than one linkset. Each signaling link cancontain both MAP and ISUP signaling.

FIG. 7 is a block diagram of a non-cross-connect deployment topology,under an embodiment. Using this alternative non-cross-connectconfiguration to achieve an active/active load-balancing mode, mapmessages routed on MGT can still be mapped into either gateway via SCCPtranslation at each GMSC-H. However if the SCCP configuration does notsupport nested modes such as (Active/Active)/Passive, then the GTTcannot be configured to fall back on real HLR when the gateway functiongoes down. However it is possible to configure the GTT at each GMSC insuch a way that the direct connected gateway is the Active SCCP entitywhile the real HLR for the SIMM MGTs is the standby/secondary SCCPentity. Since both GMSCs might be traversed evenly, this effectivelyachieves the load-balance between the Signal Gateways. However thisstill does not solve the fail-over case since if 1 gateway goes down,and the MGT-based MAP messages reach the direct connected GMSC, the realHLR will take over even though the other Signal Gateway is still alive.

For ISUP lookback signaling it should be possible to loop through theGMSC to a non-direct connected node via the other GMSC using MTP 3routing. To support fail-over (partial), each GMSC will configure 2alternate linksets for its loopback circuits. The primary link set foreach GMSC will be the one directly connected to a Signal Gateway. Thealternate link set will be the one connected to the other gateway viathe other GMSC.

The cross-connect configuration is recommended for MAP, while bothconfigurations are possible for ISUP loopback.

One embodiment of a logical cross-connection for MAP signaling virtuallyachieves the cross-connection by logically cross-connecting for SCCP butnot physically cross-connecting. As such, the GMSC1 will know wheneverSG2 is down based on the STP routing via GMSC2 so that when SPC2 isdown, GMSC1 will not route GT2 message to SPC2 via GMSC2 (primary), butroute to SPC1 (secondary) directly (no translation of called address byGMSC1 (still GT2)). When both SG1 and SG2 are down, MGT (E.214) can berouted to HLR1/2 (according to IMSI range) directly instead of routingto other GMSC to check back and forth. This backup route is just for MGTbut not necessary for MSISDN-F or GT1/GT2 because the HLRs will notrecognize it and the messages will time-out.

Furthermore, the embodiment of the logical cross-connection for MAPsignaling uses one link-set (MSC1-SPC1) to serve two route-sets (one toSPC0 and one SPC1) from MSC1 to SG1. Therefore, to a certain extent,SPC1 looks like STP for SPC0 (in other words, both SPC0 and SPC1 sharethe same MSC1-SPC1-signaling-linkset (with two physical C7 links) fromthe perspective of the GMSC).

FIG. 8 is another block diagram of a cross-connect deployment topology,under an embodiment. When the HPMN has more than two GMSCs, all theabove configurations can be used. The additional GMSC is configured toroute calls on numbers from different pools in the Signal Gatewayfunction to the two GMSCs in the cross-connect set-up. The MTP3 routingtable and GTT translation on different GMSCs is also modified to reachthe Signal Gateway function.

2.3.3. SCCP Addressing, ISUP Trunk Routing and TransformationCapabilities

One of the key functions of the Signal Gateway function is SCCP. It willuse SCCP Global Title based routing to route/re-route messages throughthe GMSC to which it is coupled (GMSC-H). TCAP (ITU-T Q.773 compliant)and MAP messages (MAP v1, v2 and v3 as documented in ETSI GSM 09.02)will be decoded and certain fields transformed (as required on acase-by-case scenario). The specific transformations are described inindividual scenarios below. The GMSC-H in HPMN also configures its GTTfunction to route MAP messages on global titles of the SIMM subscribersthrough the Signal Gateway function.

FIG. 9 is a block diagram of a Global Title Translation (GTT) routingconfiguration at a Gateway Mobile Switching Center (GMSC) in a HomePublic Mobile Network (HPMN) (GMSC-H), under an embodiment. At GMSC-H,routing on GT for each E-214 MGT range of the SIMM subscribers thatcorrespond to a HLR will need to go through the Signal Gateway. This isconfigured in a primary and 2ndary active/standby set-up. Theprimary/active SPC of this translation will be the common SPC (i.e.SPC0) of both Signal Gateways. This effectively achieves anactive/active load-balancing and fail-over support across gateways. The2ndary/standby SPC is that of the HLR for the corresponding MGT range.This allows normal local and roaming services to be retained in the rareevent of the failure of both gateways.

MAP messages on CdPA=MGT of the SIMM IMSI will be routed as normalmessages as HPMN roamers in FPMN network. That is, they can go to theexisting ISC providers, get routed in a normal way to the HPMN as aroaming subscriber in FPMN. No special configuration on FPMN GMSC-F needbe made for CdPA=MGT.

However because HPMN HLR may perform different procedures (e.g. SS suchas call barring and ODB services in VLR update, subscriber SSregistration etc) based on a SIMM subscriber's network location, theSignal Gateway need to have two types of GTs. One type is the HPMN GTwhich is what FPMN VLR will know. The other type is the FPMN GT which iswhat HPMN HLR will know when the SIMM subscriber is registered at aFPMN.

If there are multiple FPMNs involved, each Signal Gateway will have itsown corresponding FPMN GT for each FPMN. If the procedures at the HLRonly depends on whether the subscriber is outside HPMN or not, a pseudonon HPMN GT might be used by a Signal Gateway for all FPMNs as long asthe HLR procedures will regard such pseudo GT as a roaming GT.

If the HLR procedures can be configured based on VLR GT ranges, thenthere will not be a need to assign two types of GTs: HPMN and FPMN, to aSignal Gateway. The HPMN GTs of the Signal Gateways are simply regardedas roaming GTs by the HLR procedure configuration. As a result, for aSignal Gateway, its FPMN GT will be the same as its HPMN GT. Forexample, to support national roaming, an HLR is configured to indicatewhich address is a roaming GT. The SG GT can be configured like aroaming GT as if it is a roaming GT in national roaming.

Alternatively, if the HPMN network wants to regard a FPMN network as ifit is an extended home network, then again there is no need for the FPMNtype of GT for the Signal Gateway function for the FPMN network.

To support the general case, the configuration of an embodiment enablesFPMN GT support for the Signal Gateway function per FPMN. In this case,when the Signal Gateway function imitates a FPMN VLR, it will presentits FPMN GT that corresponds to the FPMN to the HPMN HLR. Whilst, whenthe Signal Gateway function imitates a HPMN HLR, it will present itsHPMN GT to the VLR-F or SGSN-F. In this way, the HPMN HLR can thendecide the right procedure to apply. When the HPMN HLR responds orinitiates a dialog with the FPMN GT associated with a Signal Gateway,the GMSC routes it to the corresponding Signal Gateway.

When the subscriber registers with a FPMN network, the MSISDN-F is usedas the calling party in delivering MO-SMS. If the message is intendedfor a non-FPMN country destination, the sending number is modified toMSISDN-H. For this reason, there will also be a special SMSC address(SMSC-S-H) used when IMSI-F is used for registration. The GMSC-H GTTtranslates the SMSC-S-H to SPC0 of the Signal Gateway. The SignalGateway determines if it needs to change the sending number MSISDN-F toMSISDN-H.

Note however since SMS will be forwarded to wherever the HLR-H indicateswhen it receives SRI-SM(MSISDN-H), then when the SIMM subscriberregisters at a FPMN, the Signal Gateway can present one of the followingthree options: (1) SG presents its HPMN GT to a HPMN HLR for VMSC andSGSN imitations; (2) SG presents FPMN GT to a HPMN HLR for VMSC and SGSNimitations in which case, the FPMN STP is configured to translate theFPMN GT in CdPA to the HPMN GT of the Signal Gateway; (3) SG passes GTof VMSC-F and SGSN-F transparently to HPMN HLR without any change. Sincea MSISDN-F is provisioned at the Signal Gateway on the HPMN side,special SCCP routing is constructed from FPMN and possibly HPMN side too(e.g., in the case of optimal routing).

FIG. 10 is a block diagram of a Global Title Translation (GTT) routingconfiguration at a Gateway Mobile Switching Center (GMSC) in a ForeignPublic Mobile Network (FPMN) (GMSC-F), under an embodiment. There arethree methods for routing MAP messages on CdPA=MSISDN-F. The first tworouting methods use the existing ISC. The first routing methodconfigures GMSC-F/STP-F GTT function on each MSISDN-F range to translatethe CdPA=MSISDN-F into the Signal Gateway function (common GT) GT0 asthe CdPA field with Routing Indicator=GT. The GTT translation for GT0will be the SPC of the ISC SCCP gateway. The rest of the SCCP routing issupported by the ISC in the method described herein.

In the second routing method, GMSC-F/STP-F configures its GTT functionon each MSISDN-F range to set its next SCCP node to the SPC of the ISCSCCP gateway on the FPMN side. The ISC SCCP gateway has 2 SPC. Oneconforms to the 24 bit SPC format of the FPMN side; while the otherconforms to the 14-bit SPC format of the ITU-T international standard.The ISC configures this SCCP gateway to route the MAP messages onCdPA=MSISDN-F to the ISC SCCP gateway that corresponds to the HPMNnetwork. The ISC SCCP gateway also has 2 SPC. One conforms to the 14-bitSPC format of the HPMN side; while the other conforms to the 14-bit SPCformat of the ITU-T international standard. This gateway configures itsGTT to route the MAP messages on MSISDN-F to the GMSC-H. All routing isdone on global title of MSISDN-F range. GMSC-H will do the finaltranslation into a routing indication on SPC/SSN as shown in the aboveGTT configuration at GMSC-H.

The third routing method routes MAP messages on MSISDN-F ranges over thededicated leased line used to route calls between GMSC-F and GMSC-H forthe SIMM service. To provide the special tariff for SIMM subscribers andavoid IDD charge, HPMN and FPMN set up a dedicated leased line betweenGMSC-F and GMSC-H. By routing MAP messages on CdPA=MSISDN-F on thededicated leased line, the HPMN can avoid configuring GTT changes on theexisting ISC gateways. While the ISC providers offer routing andtrunking as well as SS7 conversions, the HPMN also gets an SS7conversion over the leased line.

Similarly, GMSC-F also configures its ISUP trunk routing table to routeall calls on the special range of FPMN numbers (denoted by #MSISDN-F)allocated for the SIMM service towards an ISC carrier (dedicated orexisting one). The ISC carrier needs to route these calls towards theGMSC-H. FIG. 11 is a block diagram of a trunk routing configuration ofthe GMSC-F.

2.3.4. Service Node Capabilities

Service Node Capabilities are used to generate CDR for voice calls andMobile Terminated SMS. This CDR is used for appropriate rating,providing discount/rebate, billing and settlement. between the HPMN,FPMN and the SIMM subscriber. The Signal Gateway of an embodimentsupports two types of interfaces: the ISUP loopback interface and the INinterface as described below.

2.3.4.1. ISUP Loopback Interface

As described above, the Signal Gateway is capable of terminating andgenerating ISUP signaling. However, it does not have voice ports so itloops-back voice ports at the GMSC by controlling circuit allocations atthe GMSC. FIG. 12 is a block diagram of an Integrated Service DigitalNetwork (ISDN) User Part (ISUP) message loopback circuit configurationat a GMSC in a Home Public Mobile Network (HPMN) (GMSC-H), under anembodiment.

The ISUP loopback circuits of an embodiment are constructed at GMSC-H byconfiguring two E1 ports as loopback circuits such as 1-30 range ofcircuit IDs of the 1st E1 is mapped correspondingly to 33-62 range ofcircuit IDs of the 2nd E1. That is, voice path coming in on circuit ID 1will go to circuit 33 and vice versa, voice path coming in on circuit ID2 will go to circuit 34 and vice versa, and so on. While the voice pathsare looped between the two E1 ports, the signaling path is constructedat GMSC-H for both ports to be non-associatively looped through theSignal Gateway function

The Signal Gateway might also modify the calling parameter in additionto the called parameter in some cases for ISUP loopback calls. When theMIMM subscriber is called by the subscriber's FPMN number in FPMNcountry when the subscriber is in the HPMN/VPMN network, the A partynumber will be modified by the Signal Gateway to add an internationalprefix (e.g. +86 in China) after national prefix is stripped (e.g. 0 inChina). This allows the called party to easily call back. Since all theISUP loopback calls will also go through the leased line of an ISCcarrier, it is possible to perform this function by the ISC carrier. Butit is recommended to conduct this in the Signal Gateway to avoid costsand ISC complication.

Loopback circuits double the circuits used in setting up a call loopedthrough the GMSC-H with signaling via the Signal Gateway function. Sorouting through loopback circuits is carefully filtered. The differentranges of numbers from different pools of the Signal Gateway functionare configured to use loopback circuits at the GMSC-H.

2.3.4.2. IN Interface

As described above, the Signal Gateway also supports IN interface. TheIN interface is in fact more ideal than ISUP loopback since it does notincur double voice trunking or any voice trunking. However the switchmust support IN which is often not the case. Sometimes an operator isalso unwilling to or cannot deploy an IN solution due to possiblefeature interactions and switch vendor involvement.

Throughout the description herein, the ISUP loopback is used as the baseof description since it is the least common denominator of operatorswitches. Operator must be aware of the IN option which is a far morescalable solution than ISUP loopback. For this reason, a description ofthe IN interface is provided.

FIG. 13 is a block diagram of an interface between a Signal Gateway (SG)and an Intelligent Network (IN), under an embodiment. The INarchitecture involves defining triggers at the GMSC. These triggerscould be on special prefixed numbers and could even be dynamically armedfrom HLR. When the trigger criterion is satisfied, GMSC will issue INAPInitialDP (IDP) to the Signal Gateway. The Signal Gateway can issuefurther instructions such as RequestReportBCSM (RRB) to report on callevents (such as non-answer, busy, answer, disconnect etc) and CONNECT(CON) to a new number and CONTINUE (CUE). Subsequently, the switchreports events via ERB (EventReportBSCM) to the Service Node, and thereport information is used for accounting purposes and preparation of aCDR.

2.3.5. IN Interface

In addition to using the IN interface to replace ISUP loopback at HPMNas described above, the IN interface has other uses depending onoperator requirements and network environment. As one example of otheruses of the IN interface, if IN/Camel is supported at an HPMN, for SIMMsubscribers, IN or O-CSI can be defined; as such, every time the SIMMsubscriber makes a call, the IDP trigger comes to the Signal Gateway.Checks are performed to determine if the called party is a FPMN countrynumber; if it is, the SG can modify the calling party number in IN orgeneric number in Camel to be the FPMN number. For IN, the triggercriteria can be defined on FPMN country number in called party at HPMNswitches. For Camel 1+, trigger criteria can be defined on O-CSI at HLRto limit the trigger on called party being a FPMN country number prefix.IN of course can only be limited to HPMN. Camel can be applied at anyVPMN that supports Camel to HPMN.

As a second example of other uses of the IN interface, if IN/Camel issupported at FPMN, optimal routing CDR can be generated. In this case, adirect MSRN (described below) will not be issued initially to GMSC-Fwhen MSISDN-F is called and the roamer is at a non-HPMN network (FPMN orVPMN). Instead a prefixed MSRN will be returned first to the GMSC-F. TheGMSC-F can then issue an IDP on the trigger criteria of the specialprefix to the Signal Gateway via SCCP (the beauty of SCCP acrossinternational boundaries). The CON (Connect) is then issued to the realMSRN. In this way, optimal routing can be achieved with the CDR (notjust MAP SRI records) also generated by the Signal Gateway at HPMN.

In a third example of other uses of the IN interface, the IN providesthe possibility of supporting multiple HPMNs in a central location sinceISUP loopback will be prohibitively expensive when looping-back acrossinternational boundaries.

2.3.6. Redundancy and Availability of Service

Carrier-grade systems require extremely high levels of network uptime,typically 99.999%. A critical requirement in many systems is toeliminate single points of failure in SS7 links, SS7 boards, and thesystem chassis. Furthermore, systems require the ability to performhardware and software upgrades without system downtime. There are alsoredundancy requirements on software applications, data storage, andpower supplies, for example, including: redundancy in signaling datalinks (e.g. nominated reserves or switched connections); redundancy insignaling terminal devices (e.g. a common pool of terminals for the samesignaling point); redundancy of signaling links within a link set(typically operating with load sharing); redundancy in signaling routesfor each destination (possibly operating with load sharing); redundancyin signaling boards; redundancy in power supplies; redundancy insoftware application instances; redundancy in data storage; redundancyin LAN connection; and redundancy in watch dogs.

One solution as adopted by HLR/MSC which is sometimes referred to as theswitch design is to build all the above redundancy requirements within asingle chassis completely for the Signal Gateway function. One bigadvantage of this approach is that a single global title and SPC can beassigned to the Signal Gateway. There is no need to replicate dataacross gateways since TCAP transactions always return to the same node.There is also no need to replicate ISUP loopback context and callcontext. To avoid memory, disk failure and chassis damage, industrygrade hardware components will be needed. This design can be used forcore telco services such as voice call and SMS, but is overkill for theSIMM service because the failure of the Signal Gateway functions, atworst, causes SIMM subscriber services to revert back to a normal homesubscriber service (local or roaming).

Given the prohibitive cost nature of some switch designs, the SignalGateway functions of an embodiment are implemented in a server farmwhich is sometimes referred to as the server system or design. Theconfiguration of an embodiment includes two Signal Gateway serversperforming the Signal Gateway function. The two Signal Gateway serversare coupled to a database server that acts as the shared memory andshared disk for the two gateways. FIG. 14 is a block diagram of a systemincluding at least one Signal Gateway (SG) and a database, under anembodiment.

Two example server system configurations are provided herein, but manyalternative embodiments are possible. One server system configuration isbased on the Sun Netra family, while another server system configurationis based on Sun Fire family. In both cases, the use of four servers isproposed. In the Sun Netra configuration, two Netra 20 will run theSignal Gateway function while two T1405 will host a database (DB), forexample an Oracle database with replication support. In the Sun Fireconfiguration, two Sun Fire V480s host the Signal Gateway function andtwo Sun Fire V480s host the database with replication support.

The Netra 20 has four PCI slots and up to UltraSparc III 2*900 Mhzcentral processor units (CPUs) and up to 16 GB random access memory(RAM). It is designed to achieve high performance for the Signal Gatewayfunction. It has alternating current (AC) and dual direct current (DC)power options and up to 2*36 GB disk. The Netra 1405 has up to 4*440 MhzCPU, up to 8 G RAM but up to 4*36 GB hard disk and hot swappable (n+1)AC and DC power options. Netra 1405 is chosen for DB server for its highreliability and hot swappable n+1 power supplies.

The Sun Fire V480 server is configured with up to 4*900 MHz UltraSPARCIII CPUs with 8 MB of cache per processor. The Sun Fire V480 serversupports up to 32 GB of memory. All memory is accessible by anyprocessor. The Sun Fire V480 server also comes with a DVD-ROM drive, twohot-swappable (N+1) AC and DC power options, two hot-pluggable FibreChannel disks, two integrated dual 10/100/1000 Mbps Ethernet ports, andsix PCI slots, all in a 5 RU, 24-inch deep, rack-optimized chassis. TheSignal Gateway function server will also have up to 16 GB-RAM and 2*36GB disk. The database server will have up to 16 GB-RAM and 8*36 GB disk.

Each Signal Gateway has its own memory data to run the SIMM service. Thememory data contains transit information as well as persistentinformation obtained from the database or to be written to the database.The memory data is also copied to the shared memory space in thedatabase server in the case of full redundancy support. The sharedmemory can also contain the data from the DB to be accessed by eachSignal Gateway. The architecture thus forms a hierarchical level of datamanagement.

When a Signal Gateway searches for data, it first searches thecorresponding memory data. If it is not found it is going to look for itin the shared memory on the DB server and cache the data in thegateway's memory. The DB server will load the data into its memory ifthe data is in DB but not in the memory. The DB server's disk is alsoconfigured in mirrored disk structure for data redundancy.

When a Signal Gateway's memory data record has changed, a copy is madeto the DB server. This is an option to support full fail-over ifnecessary. If the DB server already had a copy from the Signal Gateway,nothing will be done. However if the DB server last had a copy fromanother gateway, the DB server will inform the other Signal Gateway toremove its copy or mark its copy for renewal. This is to solve the dataconsistency problem in a load balancing mode with full fail-oversupport.

Regardless of whether the Signal Gateway memory data is copied into theshared memory, at the end of a transaction (e.g. location update) of aSignal Gateway, data of persistent type (e.g., roaming information, CDR,etc.) is copied to the shared DB server.

FIG. 15 is a block diagram of couplings between Signal Gateways (SGs)and databases in a system, under an embodiment. If one Signal Gatewayfails, the other gateway can still function by accessing the shared DBserver. The redundancy of DB server is maintained separately and isimplemented on a high-availability machine such as Netra T1405 or SunFire V480 which have three AC and three DC hot swappable power supplies.The DB server will also have a high memory space 8-32 G RAM to supportshared memory for both gateways.

If the database server fails, the Signal Gateway function will cease tofunction (all protocol stacks will automatically be shut and all appswill not proceed until a DB connection can be established) andessentially constitute a failure of the Signal Gateway function. In thiscase, normal HLR function will take over. However the shared dataredundancy can be supported by having another replicated DB server withredundancy/fail-safe and transparent application failure support instand-by mode.

The system of an embodiment includes Oracle Net or Net 8 for transparentapplication failure (TAF). The system includes TNSNAMES.ORAconfiguration as shown below. The configuration supports transparentfail-over across multiple instances of a DB on different ports of thesame machine or across machines; it also supports load-balancing andactive/active fail-over. The fail-safe operates in active/standby modesince the failure of DB server will render the Signal Gateway functioncompletely useless. Standby mode is chosen since replication might notbe fast enough for normal cases of Signal Gateway functions although itis acceptable for exceptional cases (e.g. fail-over switch). In thisarchitecture, each Signal Gateway will open up a DB connection with theprimary DB server which replicates data to the standby DB server.

In the event of failure of the primary DB server, each gateway will openup a DB connection with the standby DB server. When the original primaryDB server is completely restored, it can become the primary serveragain. This process is automatic. Service will not be interrupted.

The original standby server (now the new primary server) will bemanually configured to synchronize with or (more precisely) replicate tothe new standby server (the original primary server). If during therestoration process of the original primary server, the new primaryserver also goes down, then the whole system fails. There will beanother alarm and no SS7 messages will be accepted; normal HLRs willtake control.

When both DB servers are down, each Signal Gateway will completely shutdown the protocol stacks to reject all SS7 messages. The applicationswill not proceed until DB connections are re-established.

To support full fail-over, shared memory data is copied to both DBservers, or the primary DB server is configured to replicate the memorydata across the standby DB server. Full fail-over support for a serviceis defined as no service interruption as long as one of two physicalgateways is functional. Partial fail-over support for a service isdefined as to include a service interruption when the gateway initiallychosen to handle the service fails but service is restored when a sparegateway is activated.

Each Signal Gateway has at least 4 PCI slots (one 33/66 MHz and three 33MHz) for peripheral IO cards. The SS7 interface cards are housed inthese slots. Each server has two disks of 36 GB each. They areconfigured in mirrored mode and hence provide high resilience.

Referring again to FIG. 6, two GMSC-Hs are used in an embodiment tocross-connect with the two physical Signal Gateways. As mentionedbefore, each gateway has its own distinguishing Global Title (GT) (GT1and GT2) and distinguishing SPC (SPC1 and SPC2). Both gateways also havea common SPC (SPC0). Link-level redundancy is achieved by using linksetswhich in some cases span across both gateways as mentioned in thedeployment topology section before.

When considering ISUP call fail-over handling, depending on thefail-over requirements, different link sets will be configured at theGMSC-H for non-associated signaling for the ISUP loopback calls. Forexample, if full fail-over is desired, then the four-link linkset thatspans across two Signal Gateways will be used for a GMSC-H'snon-associated ISUP signaling. If partial fail-over is acceptable, thenthe two two-link linksets that do not span across the two SignalGateways can be used. Note also due to the cost of ISUP loopbackcircuits, the Signal Gateways can all be coupled to one GMSC-H.

The ISUP loopback circuits of an embodiment are constructed at GMSC-H byconfiguring two (or more pairs) E1 ports as loopback circuits such as1-30 range of circuit IDs of the first E1 is mapped correspondingly to33-62 range of circuit IDs of the second E1. That is, voice path comingin on circuit ID 1 will go to circuit 33 and vice versa, voice pathcoming in on circuit ID 2 will go to circuit 34 and vice versa, and soon. There may be many pairs of E1s configured at a GMSC-H for ISUPloopback calls, depending on dimensioning requirements.

FIG. 16 is a block diagram of an ISDN User Part (ISUP) message loopbackcircuit configuration for call fail-over handling, under an embodiment.While the voice paths are looped between the two E1 ports, the signalingpath is constructed at GMSC-H for both ports to be non-associativelylooped through the Signal Gateway function using two alternate linkssets with SPC1 and SPC2 as the adjacent SPC respectively in the case ofpartial fail-over support. If GMSC is not directly connected to agateway as in the non-cross-connect configuration, then the alternatelinkset will include the adjacent GMSC. In the case of full fail-oversupport, a single link set between the GMSC-H and SPC0 can be used.However call context need be copied to the shared memory of the DBserver by each Signal Gateway.

To ensure data consistency, each time a shared memory of the DB serverobtains a copy from a Signal Gateway that differs from the last gateway,then the DB server informs the last gateway to remove its copy. Forexample, during an ISUP loopback call, signaling might first come in onegateway where call context will be created and copied to the shared DBserver. It might later go to another gateway which would need to load inthe call context from the shared DB server. The copy of the other servermust be removed to ensure data consistency. However this could introducea racing condition since the next message could go back to the originalgateway faster than its call context being removed. To avoid thisproblem for ISUP signaling, each Signal Gateway should attempt to loadthe latest if any from the shared DB server.

Since ISUP signaling runs over the same linksets as MAP signalingbetween GMSC-H and the Signal Gateway function, in the case of fullfail-over support, ISUP signaling can also be switched physicallybetween two Signal Gateways so that it can be switched to the secondSignal Gateway when the first Signal Gateway fails for some reason. Inthis way, calls can continue as if nothing had happened.

In both cases, however to protect against unexpected failures on bothnodes and to prevent fraud, ISUP signaling through the gateways aremonitored periodically to produce a temporal CDR duration every Xseconds (e.g., X=6) where X is configurable. In this way, call durationscan be accurate at least within the boundary of X seconds.

However unlike MAP signaling where a Signal Gateway can be addressed byits distinguishing global title for subsequent interactions of a MAPtransaction once the gateway is chosen in a fail-over or load-balancinginitially, the ISUP signaling interactions for the full fail-over casewill span across both physical gateways in an on-going ISUP callsession. This means copying of call context into the shared memory dataspace of the DB server by each Signal Gateway is essential if thesignaling links from a linkset spans across both physical gateways.

If the partial fail-over is acceptable (as recommended for ISUP loopbacksignaling due to the possible racing condition mentioned above), thenwhen the Signal Gateway that accepted the ISUP signaling for a loopbackcall fails, there will be no fail-over to the second gateway and thecall is simply dropped by the GMSC-H. In this case, no copy of callcontext to the DB server is required. The linksets used for the ISUPsignaling between GMSC-H and the Signal Gateway function will be twoalternate linksets (instead of one across both gateways) using thedistinguishing SPC of each gateway in primary and secondary mode. So ifthe gateway that accepted the initial ISUP signaling failed, the currentcalls get dropped. However for new ISUP loopback calls, the secondgateway will be used.

Note that when a linkset associated with a circuit call completelyfails, MTP2 level at GMSC-H of the ISUP loopback calls will inform thehigher level—ISUP level which will bring the circuit down. This avoidsthe case where a call could continue forever when the Signal Gatewaysare all down.

Next SCCP signaling fail-over support is described. Referring again toFIG. 9, the SCCP GTT configurations have been described in the SCCPconfiguration above. SCCP routing of messages (e.g. UpdateLocation) oneach MGT range of the SIMM subscribers will go through the two SignalGateways in an active/active set up at the GMSC-H, supporting bothload-sharing and fail-over. GMSC-H in this case will be configured atGTT set-up for each range of IMSI (or MGT) to go through the singlecommon SPC (SPC0) of both Signal Gateways in an effective active/activemode. The real HLR for the corresponding range of MGTs of SIMMsubscribers will be configured as a secondary backup. In the rarecondition of the entire system failing, the SIMM subscribers will roamas normal HPMN users. Note that it does not matter which gateway ischosen in the SCCP routing of messages on MGTs of SIMM subscribers.

The SCCP routing of messages (e.g. SRI, SRI-SM, etc.) based onCdPA=MSISDN-F from FPMN towards HPMN is also supported via anactive/active GTT configuration at the GMSC-H. This again achievesload-balancing and fail-over support by the Signal Gateways. Howeverunlike MGT-based routing, there will be no secondary backup for MSISDN-Fbased routing. In the rare condition of the entire system failing, theSIMM subscribers will roam as normal HPMN users and can only get homeservices (calls and SMS etc) on the HPMN number, but not on the FPMNnumber.

However because HPMN HLR may perform different procedures (e.g. SS suchas call barring and ODB services) based on a SIMM subscriber's network,the Signal Gateway has two types of GTs. One type is the HPMN GT whichis what FPMN VLR will know. The other type is the FPMN GT which is whatHPMN HLR will know when the SIMM subscriber is registered at a FPMN.

If there are multiple FPMNs involved, each Signal Gateway will have itsown corresponding FPMN GT for each FPMN. If the procedures at the HLRonly depends on whether the subscriber is outside HPMN or not, a pseudonon HPMN GT might be used by a Signal Gateway for all FPMNs as long asthe HLR procedures will regard such pseudo GT as a roaming GT.

If the HLR procedures can be configured based on VLR GT ranges, thenthere will not be a need to assign two types of GTs: HPMN and FPMN, to aSignal Gateway. The HPMN GTs of the Signal Gateways are simply regardedas roaming GTs by the HLR procedure configuration. As a result, for aSignal Gateway, its FPMN GT will be the same as its HPMN GT. Forexample, to support national roaming, an HLR is configured to indicatewhich address is a roaming GT. The SG GT can be configured like aroaming GT as if it is a roaming GT in national roaming.

Alternatively, if the HPMN network wants to regard an FPMN network as ifit is an extended home network, then again there is no need for the FPMNtype of GT for the Signal Gateway function for the FPMN network.

To support the general case, an embodiment supports a configuration toenable FPMN GT support for the Signal Gateway function per FPMN.

When the Signal Gateway function imitates an FPMN VLR, it will presentthe FPMN GT that corresponds to the FPMN to the HPMN HLR. When theSignal Gateway function imitates a HPMN HLR, it will present its HPMN GTto the VLR-F or SGSN-F. In this way, the HPMN HLR can then decide theright procedure to apply. When the HPMN HLR responds or initiates adialog with the FPMN GT associated with a Signal Gateway, the GMSCroutes it to the corresponding Signal Gateway.

Note however that since the SMS will be forwarded to wherever the HLR-Hindicates when it receives SRI-SM(MSISDN-H), then when the SIMMsubscriber registers at a FPMN, the Signal Gateway of an embodimentpresents one of the following: (1) an HPMN GT to a HPMN HLR for VMSC andSGSN imitations; an FPMN GT to a HPMN HLR for VMSC and SGSN imitationsin which case, the FPMN STP is configured to translate the FPMN GT inCdPA to the HPMN GT of the Signal Gateway; and the GT of VMSC-F andSGSN-F are passed transparently to HPMN HLR without any change.

Unlike the SCCP routing of messages based on MGT and MSISDN-F as CdPA,the SCCP routing of messages (e.g. insertSubData from HLR or ack from aVLR or forwardSMS from a SMSC) towards a GT of a Signal gateway at theGMSC-H is configured in an active-standby mode in the case of fullfail-over support. The primary DPC of the translation in this case isthe distinguishing SPC corresponding to the HPMN (if towards VLR-F) orFPMN (if towards the Signal Gateway) GT of the Signal Gateway; while thesecondary DPC is the SPC corresponding to the HPMN (if towards VLR-F) orFPMN (if towards the Signal Gateway) GT of the other gateway. In theevent of the targeted gateway failing, the second gateway willcommunicate with the originating global title using the global title ofthe first gateway.

FIG. 17 is a block diagram of updated location transaction flowfollowing Signal Gateway (SG) failure, under an embodiment. As anexample, on receiving the VLR-F's ack to insertSubData from HPMN GT1 ofthe SPC1 Signal Gateway, GMSC-H will switch over to the SPC2 of theSignal Gateway when SPC1 fails. SPC2 will assume HPMN GT1 as the callingGT when sending Ack to updateloc to VLR-F since VLR-F will only acceptthe updateLoc Ack if the calling GT is the same one as before in thetransaction.

The reason that the routing of messages on GT of a Signal Gateway is notbased on active/active set up but a active/standby setup is because thecurrent transaction context was first established at the chosen SignalGateway when messages are routed through the gateway based on MGT andMSISDN-F. Even each gateway copies the transaction context as fast as itcan over 100 Mbps Ethernet, it might not be as fast as the messagesrouted on GT of a Signal Gateway, which could be in milliseconds. Thiscould create a racing condition (similar to the ISUP signaling). Whenthe original gateway was not chosen on the current transaction context,the still-alive gateway will take longer time to load the data from theshared memory.

Therefore even in the case of full fail-over support, the transactionstill goes back with the originally chosen gateway as long as it ispossible to avoid shared DB server access. This makes it particularlyefficient for some signaling flow (e.g. SRI messaging). For cases wherethe switch-over cannot be avoided, the extra overhead introduced isstill efficient enough for fail-over handling.

In the event of a failure of the targeted gateway, the second gatewaywill take over in a full fail-over support. The second gateway will needto load the latest data from the shared DB server. In the partialfail-over support, the transaction will be dropped, and a newtransaction issued by the original calling SCCP entity.

In general, stand-alone transactions (e.g. PurgeMS, non-framedinsertSubdData etc) on the GT of a Signal Gateway as CdPA will not needto go back to the gateway since the context from the gateway will havealready been copied to the shared DB server. However since the chosen GTin CdPA of stand-along transactions is usually the result of aload-sharing transaction based on MGT and MSISDN-F as CdPA (e.g.updateLoc), the stand-alone transactions towards a particular SignalGateway will effectively be load-balanced.

It is possible to always set the GT of the Signal Gateway in the MAPcontent as a common GT between two Signal Gateways in the case of fullfail-over support. This would require each gateway to be associated withboth a distinguishing GT and a common GT. While either gateway will havethe same GT in the MAP context, the calling party or called party willbe the distinguishing GT of the gateway for the new transactioninitiated by the Signal Gateway. For example, when the chosen SignalGateway, say GT1, relays the updateLoc messages to a HLR-H, the callingGT will be GT1 but the VLR content in the message will be replaced bythe common GT GT0. This approach should achieve load-balancing slightlybetter than the case of a distinguishing GT in the MAP content forstand-alone MAP transactions. However as mentioned before, since the setof GTs of stand-alone transactions in CdPA is usually the result ofevenly distributed transactions on MGT and MSISDN-F, the finaldistribution is still fairly even. The common GT is thus not necessary.

Note that the GTT configuration at GMSC-H does not require translationfrom a global title into another global title. The translationcapability from a global title to a SPC is sufficient. The GTTconfiguration also does not assume any new translation type. Onlytranslation type 0 is used.

In reviewing the definitions of full fail-over and partial fail-oversupport described above, full fail-over support for a service type(e.g., MAP or ISUP) is defined as the current services of the servicetype not being interrupted as long as one of the two (or N) physicalgateways is functioning. Partial fail-over support for a service type isdefined to include possible partial interruptions of the currentservices when the gateway initially chosen to handle the service failsbut new services of the service type can be handled by a functioninggateway(s).

For example, if location-update fails as a result of a Signal Gatewayfailure, the MS/VLR can do a retry which will be handled correctly bythe still-alive Signal Gateway. Similarly for SMS, if the MT-SMS failsas a result of a Signal Gateway failure, the SMSC-X can initiate anothertransaction (SRI-SM followed by MT-SMS) which can then be taken over bythe functioning gateway.

For ISUP loopback calls, when a Signal Gateway fails with partialfail-over support, the call simply gets dropped. New ISUP loopback callscan be handled by the functioning gateway.

When the IN architecture is used, and a Signal Gateway fails withpartial fail-over support, the call simply gets dropped. New InitialDPrequests can be handled by the functioning gateway.

By using the shared memory and shared DB architecture betweenload-balancing gateways, the Signal Gateway function is also able tosupport full fail-over depending on the racing conditions. However dueto racing conditions, the following configuration is recommended:partial fail-over support for ISUP loopback call; partial fail-oversupport for MAP transactions; primary and standby DB servers withreplication.

This means that copying of memory data record from the Signal Gatewayfunction to the database server will not be necessary in the case ofpartial fail-over support. For purposes of the description herein, thiscopying as an option used to illustrate the case of full fail-oversupport.

It is noted that even in the case of partial fail-over support, at theend/completion of a transaction involving data of persistent nature(e.g., roaming information, CDR, etc.) in a Signal Gateway, the data issaved into the shared DB server. This means that at a later stage wherea transaction initiated by a VLR-F (e.g. SS registration,SendAuthentication etc) or by a HPMN HLR (e.g. PRN query, FSMS etc),even the Signal Gateway stored in these registers failed, based on thestandby configuration of GTT, the functioning gateway can still handlethe transaction by using the shared DB server(s).

For example, if a SIMM subscriber MSISDN-H is called when the subscriberis registered at FPMN, the HPMN HLR will query the stored Signal Gateway(since it is the VLR-F to the HLR). If the gateway failed for anyreason, the functioning gateway can still access the shared DB server(s)to locate the real VLR-F to get the MSRN information. For SMS toMSISDN-H of a SIMM subscriber at FPMN, the HPMN HLR will return thestored Signal Gateway as VMSC/SGSN where it will receive the forwardedSMS from the SMSC. If the stored gateway failed for any reason, thefunctioning gateway can still use the shared DB server(s) to handle SMSforwarding. As another example, if a SIMM subscriber performs an SSoperation when the subscriber is registered at an FPMN, the FPMN VLR-Fwill query the stored Signal Gateway (since it is the HLR to the VLR-F).If the gateway failed for any reason, the functioning gateway can stillaccess the shared DB server(s) to handle the transaction.

Therefore partial failover really means ongoing transactions will not behandled when the Signal Gateway that was processing the transactionfailed. However for completed transactions, full failover is supported.Data server redundancy is assumed here.

Referring again to FIG. 3, in addition to the signal board redundancyacross both gateways, there can also be board redundancy within eachgateway. Each gateway can host one board per PCI slot. Use of up to sixboards is possible with the Sun Fire V-480 family. Each board candistribute messages to a pool of user part app instances in a roundrobin load-sharing and fail-safe mode. Whenever an instance fails, thewatch dog will restart the instance again. There is also a unix cronthat oversees the watch dog and restarts the watch dog when it fails.The watch dog periodically monitors app instances. When an app instancefails, it is automatically removed from the configuration, and furthertraffic is processed by other app instances. After the app instance isautomatically restarted, the app instance can be reintegrated in theplatform, without interrupting traffic. Similarly, new app instances,CPU, memory, SS7 board can be added as capacity requirement increase.

When all app instances for any SS7 application protocol fail, the watchdog will terminate the SS7 stack on each DK card before it terminatesall app instances of any SS7 application protocol. This will force theGSMC-H to apply SS7 based switch-over. The watch dog then restarts allapp instances of all SS7 application protocols before restarting the SS7stack on each DK card. If an instance did not fail, but failed toproperly handle the SS7 messages intended for it, the DK board will notbe able to distribute its messages. In this case the other SignalGateway will be automatically switched over by the GMSC-H.

FIG. 18 is a block diagram of system redundancy in a system havingSignal Gateways (SGs) coupled to an Ethernet, under an embodiment. Todeal with Ethernet failure, two Ethernet buses can be configured. Eachmachine can have two IP addresses connected to the different segments ofthe LAN. Under normal operation traffic is shared between them. If onefails, all traffic is routed to the remaining Ethernet. Like SS7 links,the Ethernet buses should also be configured in a cross-connect mannerwith HPMN's IP switches.

The fact that in normal operation all components of the Signal Gatewayfunction share traffic provides major advantages over the “standby”approach, where spare components stand idle until primary componentsfail. For example the spare capacity configured into a platform can beused to handle peaks of traffic. In addition, when all the componentsare functioning, their health can be monitored: when spare componentsstand idle, monitoring and preventive maintenance is impossible.

Since each gateway is also functioning as a VLR-F to HLR-H and HLR-H toVLR-F, in the event both servers go down and Signal Gateway records arecorrupted, the information will be rebuilt using stored information inthe Signal Gateways, HLR and VLR using GSM MAP messages. In particular,the Signal Gateways will perform a periodic tape-drive backup.

Unlike a HLR or a VLR whose corruption or loss of data will only triggereither a HLR restoration or a VLR restoration but not both, thecorruption or loss of Signal Gateway data will trigger restoration atboth directions. It will first require a restart. After restoring frombackup, all affected IMSI records will need to set the purged flag andinitiate reset-VLR MAP message to the list of VLR-Fs recorded by theback up. Normal updateLocation procedure will be triggered by the VLR-Fto automatically establish roaming data in the gateways from thescratch. However providing roaming number from HLR-H to a SignalGateway, forward SMS to the Signal Gateway, SRI/SRI-SM on MSISDN-F willnot trigger MAP-Restore-Data by the Signal Gateway to the HLR-H orMAP-reset to a VLR-F. These messages will be mapped by the SignalGateway function to the real destinations VLR-F/VMSC-F/SGSN-F which canthen initiate restore data process. Signal Gateway recovery proceduresare described in more detail below.

The requirements of optimal routing of Late-Call-Forwarding also requiremaintenance of state information (mapping between FTN and temporaryFTN). Hence, it is necessary to share the in-memory information acrossthe different application servers by copying the data into the shared DBserver.

2.3.7. Scalability and Dimension

The SIMM System/Service of an embodiment is scalable based on at leastone of the following growth factors: addition of more FPMNs in multiplecountries; addition of more Multiple MSISDN subscribers; and increase inSS7 messaging traffic due to growth.

As an example, assume the following traffic model for a voice call:incoming call during busy hour (BCHA) is one call to MSISDN-H and onecall to MSISDN-F; average call duration is 90 seconds; probability ofsubscriber roaming in China is 30% (or 9 days per month); 50 k sub×(1MT-F×100% handled regardless of customer location)+(1 MT-H×30%handled)=65 k BHCA; daily call per sub=5 call to MS-H and 5 calls toMS-F; Monthly call per sub=140 call to MS-H and 140 calls to MS-F (or210 minutes each). Note that when a MAP transaction traverses through aSignal Gateway, the Signal Gateway will initiate another transaction.For example, FIG. 19 is a signal flow diagram of a voice call, under anembodiment, in which the signal flow on the MSISDN-F includes four MAPtransactions. FIG. 20 is another signal flow diagram of a voice call,under an embodiment, that includes 2 MAP transactions. It can be seenfrom the flow diagrams of FIGS. 19 and 20 that some MAP transactionsinvolve significantly more messages than others. In our followingmeasurements, a MAP transaction is assumed to include an average of fourMSUs of 200 bytes each.

Using this example, the MAP transactions through the Signal Gateway perSIMM subscriber are calculated as follows: Location update transaction=1per hour (location update and insert-sub-data etc);Send-routing-information (SRI) MSISDN-F=1 per hour; PRN for MSISDN-F andMSISDN-H=2 per hour; Provide Roaming Number transactions=1 per hour; Allother transactions (Send Authentication, SS, USSD, SRI-SM, FSM,Cancel-Loc)=3 per hour; Probability of subscriber roaming in China:30%=9 days per month; Since location update in HPMN and VPMN only gothrough Signal Gateway the first time, it takes about ¼ of the normaltransaction; 2*(1*(0.3+0.7*0.25) LocUpdate+1+2 PRN*0.3)=4.15 MAPtransactions per hour; All the rest=2*3*(0.3+0.7*0.25)=2.85 MAP perhour; MAP transaction loading in peak hour=50 k×(4.15+2.85)=50K*7=350KMAP transactions in peak hour; Total transactions(MAP+ISUP)=(350K+65000*2)=480K transactions/BH, where an ISUPtransaction is defined as all the ISUP messages within an ISUP loopbackcall (e.g., IAM in, IAM out, ACM in, ACM out, ANS in, ANS out, REL in,REL out, RLC in, RLC out, etc.).

A SIMM call is defined herein as an ISUP loopback call with signalinggoing through the Signal Gateway function. This could happen when thesubscriber gets called on MSISDN-F or when registered in FPMN.

FIG. 21 is a block diagram of a system including two Signal Gateways(SGs) and two databases, under an embodiment. As described above, twoexample system configurations are provided, including one configurationbased on the Sun Netra family, and another configuration based on SunFire family. In both configurations, four servers can be used, but theembodiment is not so limited. In the Sun Netra configuration, two Netra20 will run the Signal Gateway function while two T1405 will host thedatabases with replication. In the Sun Fire configuration, four Sun FireV480 servers are used with two servers hosting the database withreplication.

Two separate DB servers in a primary/standby set up are used instead ofloading them onto the two Signal Gateways, but numerous alternativeconfigurations are possible. This configuration improves the performanceof the Signal Gateway function as well as reduces points of failure. Forexample, if one DB server goes down, the two Signal Gateways can stillfunction in a load-sharing manner. If one Signal Gateway goes down, theDB server still has a standby available.

The Signal Gateway MAP function is built on top of the SCCP protocolstack. The TCAP layer improves performance. DK provides TCAP stack butlimited to no greater than 16K simultaneous dialogs (for both incomingand outgoing) hence the throughput.

With the Netra configuration (using 2 CPU, 2 G RAM and 2*36 disk for allmachines in the test), each Netra 20 Signal Gateway is able to supportapproximately 50 (MAP or ISUP) transactions per second. With the SunFire configuration, each V480 Signal Gateway using 2 CPU, 2 G RAM and2*36 GB disks supports approximately 50 transactions per second, roughlythe same number as Netra configuration. When using the Sun Fire 4-CPUconfiguration, each V480 Signal Gateway using 4 CPU, 4 G RAM and 2*36 GBdisks supports approximately 80 (MAP or ISUP) transactions per second.These figures increase to approximately 80 transactions per second and150 transactions per second using 2 DK cards in each Signal Gateway inthe Netra and Sun Fire configurations, respectively. Each DK card is10-bound by 4*8K bytes/s=32K bytes/s each direction, noting foursignaling links at 8K bytes per second per card.

The Netra/Sun-Fire-2-CPU configuration, therefore, can handle 180K (288Kwith two DK cards) transactions per busy hour in a simulatedenvironment. Likewise, the Sun Fire 4-CPU configuration can handle 288K(540K for 2 DK cards) transactions per busy hour or 65K BHCA per peakhour in a simulated environment.

In a complete load-balancing mode, the two-gateway configurationsupports up to 360K (or 576K in 2 DK cards) transactions per peak hourusing the Netra/Sun-Fire-2-CPU configuration and up to 576K (or 1080K in2 DK cards) transactions per peak hour using the Sun Fire 4-CPUconfiguration.

The Signal Gateway function also tracks the transaction loading of thesystem. Alarms are generated when memory, CPU, and transaction rateexceed pre-specified thresholds, say 80%. In this case, the SignalGateway can choose to reject certain type of SS7 messages, e.g. SMS sothat the sending SMSC can queue it at its end. The Signal Gateway canalso reject messages based on FPMN. The Signal Gateway can also chooseto relay for new LUP messages so the SIMM subscribers can be handled asnormal roamers as if the Signal Gateway function failed. This relay canalso be applied based on FPMN in times of system overloading.

2.4. Logistics

Deployment of the SIMM System/Service of an embodiment includes thefollowing logistics between the HPMN and FPMN. The HPMN reserves one ormore sequential block(s) of IMSI to be used for offering the service(multiple MSISDN service subscribers will have to change their SIMcards). Also, the FPMN reserves one or more sequential blocks of FPMNMSISDN-F numbers to be used by HPMN for SIMM subscribers. Further, theGMSC-F is configured to route IMSI based MGT(s) (E.214 Numbering Plan)and MSISDN-F based Global Titles (GT based on E.164 Numbering Plan) toGMSC-H through a leased line (if a leased line is used). The GMSC-F isalso configured to generate a MAP Send Routing Info (SRI) message onreceiving an ISUP with MSISDN-F as the called number/address. Inessence, the Signal Gateway acts like a HLR to the MSISDN-F for FPMN.

Continuing, the HPMN reserves four HPMN GTs and one SPC for each SignalGateway. The HPMN also reserves four FPMN GTs for each Signal Gatewayfor each FPMN supported in case the FPMN GT option is selected. Each ofthe four GTs is used to represent different types of network elements(HLR, VLR, VMSC/SGSN, GMSC/SMSC). The Signal Gateway treats these fourGTs as prefixes and appends approximately four digits afterwards tocreate four pools of GTs for dynamic assignment on the actual SignalGateway GTs. The HPMN also provides a common Signaling Point Code forall Signal Gateways and maps several Sub System Numbers (SSN) (e.g., 6,7, 8 etc) to each Signal Gateway. The GMSC-H defines routes for all SCCP(MAP) messages having CdPA as the four reserved GTs, MSISDN-F and MGTcorresponding to reserved IMSI range to a Signal Gateways.

The FPMN provides a pool of MSISDN-F numbers to HPMN. These numbers areused to route calls through the leased line between FPMN and HPMN inlate call forwarding and call rerouting for SIMM subscribers. The GMSC-Fis configured to route calls on this pool of MSISDN-F towards GMSC-Hthrough the leased line. The GMSC-H is configured to route calls on thispool using ISUP loopback circuits or IN architecture with signalingthrough a Signal Gateway.

The GMSC-H is configured to route calls over the leased line for callednumbers that belong to FPMN. It should be configured in a primary andsecondary mode such that if the leased line is down, the call routingcan still proceed over normal ISC providers.

The HPMN also provides a pool of MSISDN-H. This pool will be used by aSignal Gateway to control call-rerouting towards FPMN. GMSC-H will routeall calls on this pool using loopback circuits with signaling through aSignal Gateway.

The GMSC-H configures loopback circuits which will be used on routingall pools of numbers via ISUP loopback

The IN triggers are defined at the GMSC-H to send InitialDP to theSignal Gateway when the IN architecture is used.

If the leased line option is to be applied to all messages then, in theHPMN, the GT that corresponds to FPMN of the message is routed to GMSC-Fthrough leased line. On the FPMN side, if the GT is that of a SignalGateway, the message should be routed via the leased line.

The FPMN assigns an SPC representing GMSC-H; messages routed to this SPCare transferred via the leased line. HPMN also assigns an SPCrepresenting GMSC-F; messages routed towards this SPC are transferredvia the leased line.

If existing ISC provider to be used for MAP signaling on CdPA=MSISDN-F,GMSC-F configures GTT on CdPA=MSISDN-F in SCCP routing to set the nextSCCP destination node to the ISC providers. The ISC provider configurestheir GTT on CdPA=MSISDN-F to finally route to the GMSC-H which willroute the messages to a Signal Gateways.

Alternatively, GMSC-F/STP-F configures its GTT in such a way that forCdPA=MSSDN-F translates it to CdPA=HPMN-Common-GT-of-Signal-GW. The HPMNnetwork should be able to assign a common GT to both Signal Gateways. Itis just used logically in the translation to the common SPC of bothSignal Gateways.

If the leased line is to be used for MAP signaling on CdPA=MSISDN-F,GMSC-F configures GTT on CdPA=MSISDN-F in SCCP routing to set the nextSCCP destination node to the FPMN SPC that corresponds to the GMSC-Hover the leased line.

The ISC carries signaling and voice traffic between the HPMN and FPMN.The ISC STP for each side of the participating operators of the MultipleMSISDN service is configured to route GT on FPMN numbers (includingported-in numbers) towards the HPMN Signal Gateway. The SS7 varianttranslation (including ISUP and MAP) can be performed by a conversionfunction.

The HPMN assigns a special SMSC address (SMSC-S-H) for use as the SMSCaddress in the SIM of a SIMM subscriber. HPMN GMSC-H/GTT translates thisglobal title to the SPC of the Signal Gateway. The Signal Gatewaydetermines whether to convert the sending number (e.g., from MSISDN-F toMSISDN-H) based on the network of the SIMM subscriber and thedestination number of the recipient.

If IW-MSC is not the same as GMSC-F, then IW-MSC is configured to routemessages (in particular MAP SRI SM) to GMSC-F that in turn routesmessages to GMSC-H via a leased line.

Based on these logistics, the following GSM scenarios are describedbelow: Update Location and Insert Subscriber Data between HPMN, FPMN andVPMN; Mobile Originated Calls from SIMM subscriber in HPMN, FPMN andVPMN; Mobile Terminated Calls to SIMM subscriber in HPMN, FPMN and VPMNwhen called on MSISDN-H; Mobile Terminated Calls to SIMM subscriber inHPMN FPMN and VPMN when called on MSISDN-F; Early and Late CallForwarding in above cases for voice calls; Mobile Originated SMS fromSIMM subscriber in HPMN, FPMN and VPMN; Mobile Terminated SMS to SIMMsubscriber in HPMN, FPMN and VPMN when SMS is sent to MSISDN-H; MobileTerminated SMS to SIMM subscriber in HPMN, FPMN and VPMN when SMS issent to MSISDN-F; and supplementary services handling.

2.5. SIMM IMSI and MSISDN-F

While a new SIMM subscriber will have to change the SIM card in his/herhandset, the SIM structure remains the same as before (no dual IMSIetc), so that an operator can use its existing agreement with the SIMvendor. Furthermore, the MSISDN-H of the subscriber remains the same.Only the MSISDN-F is in a particular IMSI range, not the MSISDN-H.

The particular IMSI range allows the operator to separate SIMMsubscribers from ordinary subscribers both in terms of networkconfiguration and billing. In this way, the operator has better controlin network configuration and billing. The IMSI range also allowssignaling to be redirected thru the Signal Gateway where translationsand mappings can be applied. For example, the subscriber when registeredat FPMN will have MSISDN-F as caller ID. Another example, when thesubscriber is sending a SMS to a FPMN country number, MSISDN-F can beused as a caller ID.

Moreover, the IMSI range simplifies billing at the FPMN because it isusually based on the IMSI. The FPMN can treat CDR with the HPMN specialIMSI range as local CDRs irrespective of what MSISDN (MSISFN-F orMSISDN-H) is set at the FPMN; this ensures roaming charges are notapplied. The billing records exchange between FPMN and HPMN can be thruspecially rated TAP or CDR (MO or MT).

A special MSISDN-F range, when used, is used to simplify the FPMNnetwork GTT routing to the Signal Gateway. The Signal Gateway will actas the HLR of the MSISDN-F range. So SCCP routing on MSISDN-F will cometo the Signal Gateway either via Global Title Modification. There is noIMSI-F associated with MSISDN-F.

2.6. Roamer Information

Based on the messages that get routed via the Signal Gateway, variouspieces of information are extracted and maintained. Table 1 lists someof the key information elements extracted.

TABLE 1 Information Elements S. No. MAP MESSAGE Extracted 1. UpdateLocation IMSI, Serving MSC Address, Current VLR Address, LMSI 2. InsertSubscriber Data IMSI, MSISDN-H, Forwarding Number Information 3. UpdateLocation Response Error messages, if any and Insert Subscriber DataResponse 4. SRI for Short Message Inter-working MSC address2.7. Location Update2.7.1. SIMM Subscriber in HPMN

A VLR-H is generally configured to know the HLRs that correspond to theMGTs of all HPMN subscribers, then location update message can be issuedwith CdPA=GT-of-the-HLR with Routing Indicator set on Route on GlobalTitle. Typical GSM registration procedures are followed. The HLRincludes the true VLR address and VMSC address. The Signal Gatewayfunction is not involved.

If a VLR-H is not configured to know the HLR that corresponds to the MGTof the SIMM subscriber, then registration flow follows that of the casein VPMN. This could happen for example, when the SIMM MGT is in a newrange that is not covered in VLR-H. Rather than configuring each VLR-H,just configure the changes on GTT at the GMSC-H. A VLR-H simply routesthe messages towards a GMSC-H which can then take care of the next nodefor the messages.

2.7.2. SIMM Subscriber in FPMN

FIG. 22 is a signal flow diagram of an update location transaction,under an embodiment. The VMSC/VLR-F initiates MAP Update Locationmessage by deriving MGT (E.214) based on IMSI-H. Due to routing definedat FPMN for this MGT, the message is routed to GMSC-H, which in turnroutes it to the Signal Gateway (SG1). On receipt of the Updatelocation, the Signal Gateway carries out the transformations in Table 2.

TABLE 2 Message from Signal Gateway1 Update Location from VLR-F to HLR1SCCP Called Address: SCCP Called Address: GT: MGT GT: HLR1-H SSN: 6 SSN:6 TT: 0 TT: 0 SCCP Calling Address: SCCP Calling Address: GT: VLR-F GT:F-SG1 SSN: 7 SSN: 7 TT: 0 TT: 0 MAP level parameters: MAP levelparameters: MSC address VMSC-F MSC address: SG1/unchanged VLR addressVLR-F VLR address: F-SG1

In this table, SG1 and F-SG1 represent the HPMN GT and FPMN GT of thephysically chosen Signal Gateway by GMSC-H in its GTT function. Thus, inHLR, the Signal Gateway GT is stored as MSC and VLR address instead ofthe actual addresses. This ensures that all MAP INSERT SUBSCRIBER DATAmessages pass through the Signal Gateway and hence its contents can bemodified appropriately (for example, the MSISDN-H can be changed toMSISDN-F apart from performing routing level address changes).

Recall that to simplify the description herein, a logical SG GT is useduniformly in the call flows to represent a Signal Gateway global title.The actual physical SG GT used varies according to the implementationchoices. If a unique physical SG GT is used to correspond to eachnetwork element (e.g. HLR, VLR, VMSC etc), the correct notation isSG-network-element.

The reason that F-SG1 is introduced is because the HPMN HLR procedurecould be based on subscriber network location. For example, barring ofoutgoing calls while roaming will become barring for all outgoing callsto the VLR in the roaming network. If SG1 were a HPMN GT, then the HLRmight still think the roamer is not roaming. Another example is thatsometimes call forwarding and call barring services registration may benot allowed while roaming.

The HLR generally reacts based on Calling GT. However if the HLRprocedure reacts based on VLR address rather than calling GT and it doesnot verify if calling GT is the same as the VLR address, then thecalling GT can just be SG1 rather than F-SG1.

However if SG1 can be configured as a roaming GT in the HLR procedure orHPMN will not allow such procedure to execute with dependency on networklocation, F-SG1 will be equal to SG1. For example, to support nationalroaming, the HLR is configured to indicate which address is a roamingGT. The SG GT can be configured like a roaming GT in national roaming.

Alternatively, if HPMN regards an FPMN as an extension of its network sonot to treat the subscriber as a roamer when registered at the FPMN,then again there is no need to distinguish HPMN SG and FPMN F-SG forthis particular FPMN.

A configuration option of an embodiment enables FPMN GT support for theSignal Gateway function per FPMN, as shown in Table 3. Note that sinceSMS will be forwarded to wherever HLR-H indicates when it is queried bySRI-SM(MSISDN-H), then when the SIMM subscriber registers at a FPMN, theSignal Gateway can present at least one of the following: an HPMN GT toa HPMN HLR for VMSC imitations; an FPMN GT to a HPMN HLR for VMSCimitations in which case, the FPMN STP is configured to translate theFPMN GT in CdPA to the common HPMN GT of the Signal Gateway; and the GTof VMSC-F is passed transparently to HPMN HLR without any change(recommended).

TABLE 3 Message from Signal Gateway Insert Subscriber Data from HLR-H toVLR-F via GMSC-H SCCP Called Address: SCCP Called Address: GT: F-SG1 GT:VLR-F SSN: 7 SSN: 7 TT: 0 TT: 0 SCCP Calling Address: SCCP CallingAddress: GT: HLR1-H GT: SG1 SSN: 6 SSN: 6 TT: 0 TT: 0 MAP levelparameters: MAP level parameters: MSISDN: MSISDN-H MSISDN: MSISDN-F FTN:FTN FTN: SG-FTN

The message is routed to the FPMN VLR. The SCCP Calling Party Address isreplaced with the Signal Gateway GT. This guarantees that when the replyfor this message is sent, GMSC-H can route it to the Signal Gateway.

If Forward-To-Numbers present in the Insert Subscriber Data are not ofthe FPMN country (see below for more details) then they are modified asper policy defined for the particular FPMN. FIG. 23 is a signal flowdiagram of an update location transaction when the SIMM subscriber is inthe FPMN, under an embodiment.

Referring again to FIG. 19, the signal flow diagram depicts the flowwhen SG1 fails after insertSubData. In this case, GMSC-H switches overto SG2 via the GOO in the full fail-over case, as shown in Table 4.

TABLE 4 ISD ack from VLR-F Message from SG2 to HLR1 SCCP Called Address:SCCP Called Address: GT: SG1 GT: HLR1-H SSN: 6 SSN: 6 TT: 0 TT: 0 SCCPCalling Address: SCCP Calling Address: GT: VLR-F GT: F-SG1 SSN: 7 SSN: 7TT: 0 TT: 0

The SG2 will continue the transaction using the context loaded from theshared memory data of the DB server which was copied by SG1 each timeits memory data record changed, as shown in Table 5. From the context,SG2 will still use SG1 in communicating back with HLR-H and VLR-F.UpdateLoc Ack proceeds from HLR-H to SG1 and SG1 to VLR-F as if nothinghappened to SG1 although the physical gateway to handle the transactionnow is really associated with SG2.

TABLE 5 Message from SG2 to VLR-F Update LOC ack from HLR-H via GMSC-HSCCP Called Address: SCCP Called Address: GT: SG1 GT: VLR-F SSN: 7 SSN:7 TT: 0 TT: 0 SCCP Calling Address: SCCP Calling Address: GT: HLR1-H GT:SG1 SSN: 6 SSN: 6 TT: 0 TT: 0 HLR number: HLR1-H HLR number; SG-HLR1-H

FIG. 24 is a signal flow diagram of an update location transactionfollowing failure of a Signal Gateway (SG), under an embodiment. Thissignal flow diagram shows the message flow in the event of a failure ofSG1. After a successful location update transaction, the context isremoved from the memory after roamer information is extract into roamerDB.

2.7.3. SIMM Subscriber in VPMN

The VMS C/VLR-V generates MGT based on IMSI-H in MAP Update Locationmessage. Due to routing defined at GMSC-V for this MGT, the message isrouted to GMSC-H, which in turn routes it to a Signal Gateway.

There will be a forbidden VPMN table for each group of IMSIs. Forexample, if HPMN can get discount for one specific IMSI range from FPMN,this range will not register with any operators in the same country asFPMN.

The Signal Gateway determines if the user is allowed to roam inVPMN/VLR. If the user is not allowed to roam in this VPMN/VLR (in acountry with FPMN, for example), the Update Location request will berejected and not forwarded or responded to. The Signal Gateway can alsohave flexible logic to accept initially rejected VPMN/VLR based on retryattempts and intervals between attempts. If the user is allowed to roamin this VPMN (in a country with no FPMN, for example), the SignalGateway sends the message without modification and hence the HLR storesthe true VLR and VMSC addresses in VPMN. Further interaction bypassesthe Signal Gateways.

If the Signal Gateway function fails anyway, the GMSC-H will switch overto HLR-H completely via its GTT configuration. In this case, normalservices (roaming voice and SMS, etc.) continue to function as if theSignal Gateway function does not exist. Services on MSISDN-F (e.g. callsand SMS) however will not function in this case.

2.7.4. Registration Option

The Signal Gateway of an embodiment can be configured to store themapping of VMSC and VLR for SIMM subscribers registering at HPMN andVPMN. This information can be used to change caller ID when the SIMMsubscriber is making a call to a FPMN country number. The SIMMsubscriber can use a USSD command to toggle caller ID depending on thedestination country he/she is calling. He/she can also use this functionto mask his/her location.

2.8. Mobile Originated Calls

2.8.1. SIMM Subscriber in HPMN

No change in normal GSM procedures.

2.8.2. SIMM Subscriber in FPMN

The MAP INSERT SUBSCRIBER DATA message that was sent from HLR to VLR-Fvia the Signal Gateway is modified to have MSISDN-F as the caller ID,under an embodiment. Thus, all calls and SMS messages that originate inFPMN send MSISDN-F as CLI.

In order to make best utilization of the leased line, if possible,GMSC-F should be configured to route calls to HPMN via the leased line.The routing criteria could be based on caller IMSI range and destinationnumber in HPMN. Additionally, it is possible to configure the systemsuch that if the Caller ID is guaranteed over the leased line and thedestination number is not in FPMN (e.g., an HPMN number in particular),the SS7 converter of an ISC carrier can change the CLI from MSISDN-F toMSISDN-H during ISUP variant conversions between FPMN and HPMN. Thisprovides the subscriber the privacy they may desire in not lettingpeople know they are roaming in an FPMN. Perhaps more importantly, theHPMN recipients can recognize who called since they are more familiarwith the HPMN numbers.

Generally, when both the HPMN and FPMN support Camel and the subscriberhas O-CSI, the gsmSCF address of the O-CSI will be the GT of the SignalGateway. The O-CSI need only be loaded when the subscriber registeredwith FPMN. In this way, every time the subscriber at FPMN makes a callthe O-CSI trigger issues InitialDP to the Signal Gateway which checksagainst the destination number and issues Connect with a new callingparty if the caller ID is to be changed to MSISDN-H. Otherwise, if thesubscriber calls a FPMN number, CONTINUE will be issued.

Since Camel is not supported in many networks, changes to the caller IDbased on destination numbers rely on USSD commands sent to the SignalGateway. For example, “**123*0#” shows the current caller ID; “**123*1#”toggles the caller ID between HPMN and FPMN; “**123*2#” informs theSignal Gateway not to automatically change caller ID; “**123*3#” informsthe Signal Gateway to automatically change the caller ID. When thetoggle USSD command is sent to the Signal Gateway, it issuesInsertSubscriberData with the alternative caller ID to the real VLR. TheUSSD toggle can be applied in any VPMN and FPMN networks or can belimited to FPMN networks. The SIMM subscribers can also use the USSDtoggle to mask their location with regard to the caller ID.

The originating MSC will generate a CDR with IMSI and MSISDN-F/MSISDN-H.The FPMN billing system should be able to rate these CDRs by looking atIMSI or MSISDN-F which is in a special range. In the case where a SignalGateway outage occurs before an Update Location, the CDR will containMSISDN-H along with the IMSI. However the FPMN billing system shouldstill view this specially. The records are rated by FPMN and sent inspecial TAP/CDR files to HPMN.

2.8.3. SIMM Subscriber in VPMN

No change in normal GSM procedures.

2.9. Mobile Terminated Calls

2.9.1. SIMM Subscriber in HPMN

Calls to an MSISDN-H are normally routed and the subscriber is chargedlocal MT call charges.

Calls to MSISDN-F are routed via the leased line. GMSC-F is configuredto issue or transfer a MAP SRI request towards the Signal Gateway usingMSISDN-F as SCCP Called Party Address. This accommodates the case wherethe originating MSC (e.g., VMSC-F) might directly issue the SRI althoughthe SRI is routed to the GMSC-F. The Signal Gateway transforms the SRImessage as shown in Table 6.

TABLE 6 Message from Signal Gateway Send Routing Info from GMSC-F toHLR-H via GMSC-H SCCP Called Address: SCCP Called Address: GT: MSISDN-FGT: MSISDN-H SSN: 6 SSN: 6 TT: 0 TT: 0 SCCP Calling Address: SCCPCalling Address: GT: GMSC-F GT: SG SSN: 8 SSN: 8 TT: 0 TT: 0 MAP levelparameters: MAP level parameters: MSISDN: MSISDN-F MSISDN: MSISDN-H

Note that the calling address of the Signal Gateway is SG not F-SGbecause, in this case, it is imitating a HPMN GMSC.

The SRI message is hence rerouted to the HLR that has information onMSISDN-H. HLR issues a MAP PRN message directed to VLR-H and gets MSRNin response. HLR returns MSRN-H in the SRI response back to the SignalGateway. Signal Gateway transforms the message as shown in Table 7.

TABLE 7 Message from Signal Gateway Send Routing Info Response fromHLR-H to GMSC-F via GMSC-H SCCP Called Address: SCCP Called Address: GT:SG GT: GMSC-F SSN: 8 SSN: 8 TT: 0 TT: 0 SCCP Calling Address: SCCPCalling Address: GT: HLR-H GT: SG SSN: 6 SSN: 6 TT: 0 TT: 0 MAP levelparameters: MAP level parameters: MSRN: MSRN-H MSRN: #MSRN-H

The #MSRN-H is a notation that denotes a number whose mapping to MSRN-His maintained in the Signal Gateway function. The actual number couldjust be that where the symbol ‘#’ is again a logical notation that candenote “#”, “999” or some prefixes. The actual number could also be thatof the pool of FPMN MSISDN-F that corresponds to the MSISDN-F called.For example, if the MSISDN-F is a Beijing Mobile number, the pool shouldbe filtered to present a Beijing Mobile number to establish the mapping.

While reducing the use of FPMN numbers, the actual use of a prefix forthe notation #MSRN-H could be logistically challenging in cases whereevery VMSC (e.g., for calls originated in FPMN network) can issue SRIquery (e.g., China Mobile) since there might be hundreds if notthousands of VMSCs that require configuring to route the call via theleased line. The FPMN # pool choice on the other hand will cause theSRI-issuing VMSC (if not the GMSC-F itself, including those with optimalrouting capability) to route the call at least to the GMSC-F for thechosen number from the pool. Only the GMSC-F will be configured to routethe call over the leased line.

Another challenge for the prefix-based approach is that it might exceedboth MAP and ISUP length for a FPMN. The pool-based approach does notsuffer this problem.

If VMSC-F is the SRI-issuing node, then VMSC-F will route the call toGMSC-F. GMSC-F is configured to route the call via the leased line toGMSC-H based on #MSRN-H. GMSC-H is configured to send ISUP IAM messageto the Signal Gateway based on the destination number. The voice trunksare held at GMSC-H. Signal Gateway maps the destination number to thereal MSRN and routes the call back to the GMSC-H. GMSC-H routes the callto the terminating VMSC-H.

The Signal Gateway also examines the A-party number after receiving theISUP loopback signaling from GMSC-H. If the A party number is a nationalnumber and the SRI-issuing node is a FPMN node, then the A partynational prefix is stripped before prefixing the rest of the A partynumber with the international prefix of FPMN; otherwise A is prefixeddirectly with the international prefix of FPMN. For example, assumingFPMN is China Mobile, the following modifications will be performed: ifthe first digit of the A party is 0, the first digit is stripped off andthe rest of A is prefixed with +86 (i.e change address indicator tointernational and prefix with 86 as addressing signal digits); if thefirst digit of the A party is 1, A is prefixed with +86 (i.e changeaddress indicator to international and prefix with 86 as addressingsignal digits).

FIG. 25 is a signal flow diagram of mobile terminated calls when theSingle IMSI Multiple MSISDN (SIMM) subscriber is in a HPMN, under anembodiment, including the signaling trace for a call involving a normalflow of SRI. FIG. 26 is another signal flow diagram of mobile terminatedcalls when the SIMM subscriber is in a HPMN, under an embodiment.

The originating MSC will generate a Mobile Originated CDR. VMSC-H willgenerate a MT CDR and use it to compute local air-time charges for theSIMM subscriber. GMSC-F and GMSC-H will generate additional transit CDR.Signal Gateway will generate CDR that will be used by the HPMN billingsystem in order to add special roaming re-routing charges to the SIMMsubscriber's bill over and above charges computed using VMSC MT CDR. Ifthere are multiple FPMNs, it is possible to identify which FPMNoriginated the call since the CDR contains the chosen FPMN number and/orthe SRI-issue VMSC-F/GMSC-F address. In addition, HPMN and FPMN maysettle charges for calls routed via the leased line.

FIG. 27 is a signal flow diagram of mobile terminated calls when theSIMM subscriber is in a HPMN and a Signal Gateway (SG) fails, under anembodiment. This signal flow diagram depicts the SRI flow when SG1breaks down after SRI-ACK is issued from HLR-H. FIG. 28 is anothersignal flow diagram of mobile terminated calls when the SIMM subscriberis in a HPMN and a Signal Gateway (SG) fails, under an embodiment. Thesignal trace of FIG. 28 includes the case of full fail-over support.FIG. 29 is yet another signal flow diagram of mobile terminated callswhen the SIMM subscriber is in a HPMN and a Signal Gateway (SG) fails,under an embodiment.

Note that at the end of the MAP transaction before the ISUP transaction,the data (e.g., #MSRN, MSRN) associated with the MAP transaction iswritten to the shared DB server. There is a grace period for this datamaintained in the transit in the gateway in case the ISUP loopbacksignaling indeed goes back to the gateway. However because the data isalso shared in the DB server, the ISUP signaling can also go to theother server in which case the data will be read from the shared DBserver.

Thus even in the case of partial fail-over, when SG1 failed aftercompleting the MAP transaction but just before the ISUP loopback case,SG2 continues to function by reading the data (e.g., #MSRN, MSRN) fromthe DB server.

Note also that the pool of #MSRN-H is shared not split by SG1 and SG2.Besides, it is assumed that the MSC will route all ISUP and SCCP havinga called number that matches numbers in a dedicated range of MSISDN-Fand #MSRN-H to SG1/SG2. The architecture of an embodiment does not sendany ISUP or SCCP message having a called number in the same range ofMSISDN-F or #MSRN-H back to MSC.

An example CDR algorithm for a successful call is as follows (there areadditional fields added by the Signal Gateway, e.g. the SRI-issuing MSCaddress, the prefixed MSRN information, etc.):

Roaming call (ROAM): ROAM_CALL_REFERENCE CallRef (#MSRN)ROAM_EXCHANGE_ID SG ROAM_NUMBER_OF_SS_RECORDS 00 ROAM_CALLING_NUMBERCC|NDC|A (A#) ROAM_CALLED_IMSI MCC|MNC|MSIN (SIMM subscriber IMSI)ROAM_CALLED_NUMBER NDC|B (SIMM MSISDN-F) ROAM_CALLED_MSRN NDC|msrnROAM_IN_CIRCUIT_GROUP BSC_CCT(loopback in circuit group) ROAM_IN_CIRCUITBSC_CCT(loopback in circuit) ROAM_OUT_CIRCUIT_GROUP TRUNK_CCT(loopbackout circuit group) ROAM_OUT_CIRCUIT TRUNK_CCT(loopback out circuit)ROAM_BASIC_SERVICE_TYPE 00 (tele serv.) ROAM_BASIC_SERVICE_CODE 11(telephony) ROAM_FACILITY_USAGE 00000000 ROAM_CAUSE_FOR_TERMINATION00000000 ROAM_CALL_TYPE 03 (outgoing) ROAM_ROAM_MCZ_TARIFF_CLASS MCZ(msrn) ROAM_ROAM_MCZ_PULSES 0000 ROAM_CALLED_MSRN_TON 06 (national)ROAM_CALLED_MSRN_NPI 05 (isdn) ROAM_CALLING_NUMBER_TON 05 (internat.)ROAM_CALLING_NUMBER_NPI 05 (isdn) ROAM_CALLED_NUMBER_TON 05 (internat.)ROAM_CALLED_NUMBER_NPI 05 (isdn) ROAM_LEG_CALL_REFERENCE CallRef G MSRNROAM_CALLED_MSRN-2 CC|NDC|msrn-f (#MSRN) ROAM_CALLED_MSRN-2_TON 05(internat.) ROAM_CALLED_MSRN-2_NPI 05 (isdn) ROAM_SRI-ISSUING-MSC:CC|NDC|msc (sri-issuing MSC-F) ROAM_SET_UP_START_TIMEROAM_IN_CHANNEL_ALLOCATED_TIME ROAM_OUT_CHANNEL_ALLOCATED_TIMEROAM_B_IDLE_TIME ROAM_ANSWER_TIME ROAM_CHARGING_START_TIMEROAM_CHARGING_END_TIME ROAM_ROAM_MCZ_DURATION2.9.2. SIMM Subscriber in FPMN2.9.2.1. Calls to a Voicemail-F

When the SIMM subscriber is in an FPMN country, the subscriber can callan FPMN-F number to check home voicemail; the GMSC-F routes this callover the dedicated leased line to the GSMC-H which can loopback the callsignaling through the Signal Gateway function if billing by the SignalGateway is desired. The Signal Gateway will add the correspondingvoicemail number (e.g., 19xxx, CSL internal voicemail routing) to routeback to the GSMC-H. Alternatively this can be all handled by GMSC-H viaswitch translation to avoid loopback circuits.

Caller ID will be altered by the Signal Gateway function to be MSISDN-H.If caller ID is received by the voicemail system at HPMN, only the PINis requested (if set); otherwise the voicemail box number is alsoprompted.

2.9.2.2. Mobile Terminated Call on MSISDN-H

Calls to MSISDN-H are routed from GMSC-H to VMSC-F via the leased line.GMSC-H issues a MAP SRI command to the HLR with SCCP Called PartyAddress as MSISDN-H. Note that during the Update Location from FPMN, themessage was routed via the Signal Gateway and the HLR contains theaddress of the Signal Gateway rather than the true VLR address. Hence,the HLR issues a MAP PRN request to the Signal Gateway. The SignalGateway transforms the PRN as shown in Table 8.

TABLE 8 Message from Signal Gateway Provide Roaming Number from HLR-H toVLR-F via GMSC-H SCCP Called Address: SCCP Called Address: GT: F-SG GT:VLR-F SSN: 7 SSN: 7 TT: 0 TT: 0 SCCP Calling Address: SCCP CallingAddress: GT: HLR-H GT: SG SSN: 6 SSN: 6 TT: 0 TT: 0

The message is routed to the FPMN and the Signal Gateway modifies thePRN response as shown in Table 9.

TABLE 9 Provide Roaming Number Response Message from Signal Gateway fromVLR-F to HLR-H via GMSC-H SCCP Called Address: SCCP Called Address: GT:SG GT: HLR-H SSN: 6 SSN: 6 TT: 0 TT: 0 SCCP Calling Address: SCCPCalling Address: GT: VLR-F GT: F-SG SSN: 7 SSN: 7 TT: 0 TT: 0 MAP levelparameters: MAP level parameters: MSRN: MSRN-F MSRN: #MSRN-F

Again #MSRN-F is simply a notation that denotes a number whose mappingto MSRN-F is maintained in the Signal Gateway function. The actualnumber could just be that where the symbol ‘#’ is again a logicalnotation that can denote “#”, “999” or some prefixes. The actual numbercould also be that of the pool of HPMN MSISDN-H.

While reducing the use of the HPMN numbers, the actual use of a prefixfor the notation #MSRN-F could introduce length problem to both MAP andISUP messages since MSRN-F is issued by the FPMN network. The HPMN #pool choice on the other hand does not have the problem at the expensiveof consuming more HPMN numbers.

GMSC-H is configured to send ISUP IAM messages to the Signal Gatewaybased on the #MSRN-F destination number. The voice trunks are held atGMSC-H. Signal Gateway maps the destination number to the real MSRN-Fand routes the call back to the GMSC-H.

The Signal Gateway also examines the A-party number after receiving theISUP loopback signaling from GMSC-H. If the A party number is a nationalnumber and the PRN-issuing node is a HPMN node, then the A party has anational prefix which is stripped before prefixing the rest of A withthe international prefix of HPMN; otherwise A is prefixed directly withthe international prefix of HPMN.

The GMSC-H is configured to route the call via the leased line to GMSC-Fbased on MSRN-F being a number in FPMN. GMSC-F then routes the call tothe terminating VMSC-F. Note that GMSC-H here did not distinguish MSRN-Fgenerated as a result of SIMM roamers from normal roamers in FPMN.GMSC-H is configured to route all calls to FPMN numbers using the leasedline. This is to increase the use of the leased line to cut down costsassociated with IDD charges paid to the ISC providers.

To avoid congestion and to support fail-over, the GMSC-H shouldconfigure the routing towards FPMN side using a primary/secondarysetting. The primary route in this case will be the leased line whilethe secondary standby route will be that of the existing ISC providers.

FIG. 30 is a signal flow diagram of mobile terminated calls on aMSISDN-H when the SIMM subscriber is in a FPMN, under an embodiment.Note that the pool of #MSRN-F is shared not split by SG1 and SG2.Besides, it is assumed MSC will route all ISUP and SCCP with callednumber in a dedicated range of #MSRN-F to SG1/SG2. The architecture ofan embodiment does not send any ISUP or SCCP message having a callednumber in the same range of #MSRN-F back to MSC.

The FPMN VMSC generates MT CDR using IMSI and MSISDN-F. It is billed ata special pre-negotiated rate and sent via TAP. The CDR generated bySignal Gateway is used for adding roaming call re-routing charges. TheCDR has the record of the assigned HPMN # from the HPMN # pool whichindicates the call origination side and the destination MSRN-F whichindicates the call destination side. An example CDR algorithm is asfollows:

Roaming call (ROAM): ROAM_CALL_REFERENCE CallRef (#MSRN-F)ROAM_EXCHANGE_ID SG ROAM_NUMBER_OF_SS_RECORDS 00 ROAM_CALLING_NUMBERCC|NDC|A (A#) ROAM_CALLED_IMSI MCC|MNC|MSIN (SIMM subscriber IMSI)ROAM_CALLED_NUMBER NDC|B (SIMM MSISDN-H) ROAM_CALLED_MSRN NDC|msrn(msrn-F) ROAM_IN_CIRCUIT_GROUP BSC_CCT(loopback in circuit group)ROAM_IN_CIRCUIT BSC_CCT(loopback in circuit) ROAM_OUT_CIRCUIT_GROUPTRUNK_CCT(loopback out circuit group) ROAM_OUT_CIRCUIT TRUNK_CCT(loopback out circuit) ROAM_BASIC_SERVICE_TYPE 00 (tele serv.)ROAM_BASIC_SERVICE_CODE 11 (telephony) ROAM_FACILITY_USAGE 00000000ROAM_CAUSE_FOR_TERMINATION 00000000 ROAM_CALL_TYPE 03 (outgoing)ROAM_ROAM_MCZ_TARIFF_CLASS MCZ (msrn-F) ROAM_ROAM_MCZ_PULSES 0000ROAM_CALLED_MSRN_TON 05 (international) ROAM_CALLED_MSRN_NPI 05 (isdn)ROAM_CALLING_NUMBER_TON 06 (nat.) ROAM_CALLING_NUMBER_NPI 05 (isdn)ROAM_CALLED_NUMBER_TON 06 (nat.) ROAM_CALLED_NUMBER_NPI 05 (isdn)ROAM_LEG_CALL_REFERENCE CallRef G MSRN ROAM_CALLED_MSRN-2 CC|NDC|msrn-H(#MSRN-F) ROAM_CALLED_MSRN-2_TON 06 (nat.) ROAM_CALLED_MSRN-2_NPI 05(isdn) ROAM_SRI-ISSUING-MSC: CC|NDC|msc (sri-issuing MSC-H)ROAM_SET_UP_START_TIME ROAM_IN_CHANNEL_ALLOCATED_TIMEROAM_OUT_CHANNEL_ALLOCATED_TIME ROAM_B_IDLE_TIME ROAM_ANSWER_TIMEROAM_CHARGING_START_TIME ROAM_CHARGING_END_TIME ROAM_ROAM_MCZ_DURATION2.9.2.3. Mobile Terminated Call on MSISDN-F

Calls to the MSISDN-F are routed to GMSC-F. GMSC-F is configured toissue or transfer a MAP SRI query to the Signal Gateway with SCCP CalledParty Address as MSISDN-F. Note this transfer includes the case wherethe originating MSC (e.g. VMSC-F) might directly issue the SRI which isrouted to GMSC-F.

The GMSC-F routes the message to GMSC-H which then passes the messageson to the Signal Gateway SG1 via GTT. SG1 then forwards the SRI query tothe real HLR. Note that GMSC-F can either route SCCP messages onMSISDN-F towards HPMN side via an ISC provider which is configured toroute the CdPA=MSISDN-F towards the HPMN side or it is configured in itsown GTT (of STP-F/GMSC-F) to translate CdPA=MSISDN-F toCdPA=Common-HPMN-GT-of-Signal-Gateway.

FIG. 31 is a signal flow diagram of mobile terminated calls on aMSISDN-F when the SIMM subscriber is in a FPMN, under an embodiment.Note that during the Update Location from FPMN, the message was routedvia the Signal Gateway and the HLR contains the address of the SignalGateway rather than the true VLR address. Hence, the HLR issues a MAPPRN request to the Signal Gateway. The Signal Gateway transforms the PRNas shown in Table 10.

TABLE 10 Message from Signal Gateway Provide Roaming Number from HLR-Hto VLR-F via GMSC-H SCCP Called Address: SCCP Called Address: GT: F-SGGT: VLR-F SSN: 7 SSN: 7 TT: 0 TT: 0 SCCP Calling Address: SCCP CallingAddress: GT: HLR-H GT: SG SSN: 6 SSN: 6 TT: 0 TT: 0

The message is routed to the FPMN and the Signal Gateway modifies thePRN response as shown in Table 11.

TABLE 11 Provide Roaming Number Response Message from Signal Gatewayfrom VLR-F to HLR-H via GMSC-H SCCP Called Address: SCCP Called Address:GT: SG GT: HLR-H SSN: 6 SSN: 6 TT: 0 TT: 0 SCCP Calling Address: SCCPCalling Address: GT: VLR-F GT: F-SG SSN: 7 SSN: 7 TT: 0 TT: 0 MAP levelparameters: MAP level parameters: MSRN: MSRN-F MSRN: #MSRN-F

Here #MSRN-F is a notation that denotes a number whose mapping to MSRN-Fis maintained in the Signal Gateway function. The actual number couldjust be that where the symbol ‘#’ is again a logical notation that candenote “#”, “999” or some prefixes. The actual number could also be thatof the pool of FPMN MSISDN-F that corresponds to the MSISDN-F called.For example, if the MSISDN-F is a Beijing Mobile number, the pool shouldbe filtered to present a Beijing Mobile number to establish the mapping.

While reducing the use of the number of FPMN numbers, the actual use ofa prefix for the notation #MSRN-F could be logistically challenging incases where every VMSC (e.g., for calls originated in FPMN network) canissue SRI query (e.g., China Mobile) since there might be hundreds ifnot thousands of VMSCs will need be configured to route the call via theleased line. The FPMN # pool choice on the other hand will cause theSRI-issuing VMSC (if not the GMSC-F itself, including those with optimalrouting capability) to route the call at least to the GMSC-F for thechosen number from the pool. Only the GMSC-F will then be configured toroute the call over the leased line.

The GMSC-F is configured to route the call via the leased line to GMSC-Hbased on #MSRN-F. GMSC-H is configured to send ISUP IAM message to theSignal Gateway function based on the destination number. The voicetrunks are held at GMSC-H. The chosen Signal Gateway maps thedestination number to the real MSRN-F and routes the call back to theGMSC-H. GMSC-H routes the call to GMSC-F which will then route the callto the terminating VMSC-F.

In this case, the Signal Gateway leaves A-party information unchanged.

FIG. 32 is another signal flow diagram of mobile terminated calls on aMSISDN-F when the SIMM subscriber is in a FPMN, under an embodiment. TheFPMN VMSC generates MT CDR using IMSI and MSISDN-F. It is billed at aspecial pre-negotiated rate and sent via TAP. The CDR generated by theSignal Gateway is used for adding roaming call re-routing charges; anexample CDR algorithm is as follows:

Roaming call (ROAM): ROAM_CALL_REFERENCE CallRef (#MSRN-F)ROAM_EXCHANGE_ID SG ROAM_NUMBER_OF_SS_RECORDS 00 ROAM_CALLING_NUMBERCC|NDC|A (A#) ROAM_CALLED_IMSI MCC|MNC|MSIN (SIMM subscriber IMSI)ROAM_CALLED_NUMBER NDC|B (SIMM MSISDN-F) ROAM_CALLED_MSRN NDC|msrn(msrn-F) ROAM_IN_CIRCUIT_GROUP BSC_CCT(loopback in circuit group)ROAM_IN_CIRCUIT BSC_CCT(loopback in circuit) ROAM_OUT_CIRCUIT_GROUPTRUNK_CCT(loopback out circuit group) ROAM_OUT_CIRCUITTRUNK_CCT(loopback out circuit) ROAM_BASIC_SERVICE_TYPE 00 (tele serv.)ROAM_BASIC_SERVICE_CODE 11 (telephony) ROAM_FACILITY_USAGE 00000000ROAM_CAUSE_FOR_TERMINATION 00000000 ROAM_CALL_TYPE 03 (outgoing)ROAM_ROAM_MCZ_TARIFF_CLASS MCZ (msrn-F) ROAM_ROAM_MCZ_PULSES 0000ROAM_CALLED_MSRN_TON 05 (international) ROAM_CALLED_MSRN_NPI 05 (isdn)ROAM_CALLING_NUMBER_TON 05 (internat.) ROAM_CALLING_NUMBER_NPI 05 (isdn)ROAM_CALLED_NUMBER_TON 05 (internat.) ROAM_CALLED_NUMBER_NPI 05 (isdn)ROAM_LEG_CALL_REFERENCE CallRef G MSRN ROAM_CALLED_MSRN-2 CC|NDC|msrn-F(#MSRN-F) ROAM_CALLED_MSRN-2_TON 06 (internat.) ROAM_CALLED_MSRN-2_NPI05 (isdn) ROAM_SRI-ISSUING-MSC: CC|NDC|msc (sri-issuing MSC-F)ROAM_SET_UP_START_TIME ROAM_IN_CHANNEL_ALLOCATED_TIMEROAM_OUT_CHANNEL_ALLOCATED_TIME ROAM_B_IDLE_TIME ROAM_ANSWER_TIMEROAM_CHARGING_START_TIME ROAM_CHARGING_END_TIME ROAM_ROAM_MCZ_DURATION

Since roamer information (e.g., VMSC-F, VLR-F, IMSI-H) at FPMN ismaintained in the Signal Gateways the Signal Gateway can also directlyissue PRN to VLR-F when receiving SRI/SRI-SM query on the FPMN MSISDN-Fnumber under certain conditions (e.g., CFU indicator is not set, thereis no incoming call barring, there is no T-CSI service) rather thanlooped back through the HLR-H. However if any of the special conditionsare present for the SIMM subscriber, the Signal Gateway will not havethe HLR-H knowledge for those conditions since they will not be sent tothe Signal Gateway when functioning as a VLR to HLR-H; in that case, theSignal Gateway will relay SRI to HLR-H and cannot directly issue PRNquery to VLR-F even if it knows the VLR-F.

In Table 12, the SG1 is assumed to directly issue the PRN query toVLR-F, and optimal routing and fail-over support is described.

TABLE 12 PRN Message from Signal Send Routing Info from GMSC-F Gatewayto GMSC-H SCCP Called Address: SCCP Called Address: GT: MSISDN-F GT:VLR-F SSN: 6 SSN: 6 TT: 0 TT: 0 SCCP Calling Address: SCCP CallingAddress: GT: GMSC-F GT: SG1 SSN: 8 SSN: 8 TT: 0 TT: 0 MAP levelparameters: MAP level parameters: MSISDN: MSISDN-F MSISDN: MSISDN-FIMSI: IMSI -H

Note that MSISDN is an optional parameter in the request. GMSC-H routesthe PRN to GMSC-F which then routes the message to the VLF-F. The VLR-Freturns MSRN-F in the response to SG1. SG1 returns #MSRN-F to GMSC-F orthe original SRI-issuing VMSC-F, as shown in Table 13.

TABLE 13 Provide Roaming Number Response Response from SG1 to GMSC-Ffrom VLR-F to SG1 or SRI-issuing VMSC-F SCCP Called Address: SCCP CalledAddress: GT: SG1 GT: GMSC-F SSN: 6 SSN: TT: 0 TT: 0 SCCP CallingAddress: SCCP Calling Address: GT: VLR-F GT: SG1 SSN: 7 SSN: 7 TT: 0 TT:0 MAP level parameters: MAP level parameters: MSRN: MSRN-F MSRN: #MSRN-F

FIG. 33 is yet another signal flow diagram of mobile terminated calls ona MSISDN-F when the SIMM subscriber is in a FPMN, under an embodiment.

Now consider the case in which SG1 failed after or during theestablishment of the call as depicted below. MTP level of switch canstill change over to SG2. This is possible due to the channelnon-associating signaling of the ISUP loopback set up.

FIG. 34 is a signal flow diagram of mobile terminated calls on aMSISDN-F when the SIMM subscriber is in a FPMN and a Signal Gateway (SG)fails, under an embodiment. This signal flow shows the generic flow ofthe ISUP loopback when SG1 failed. For example, when IAM message on#MSRN-F reaches the GMSC-H, it is looped through the loopback circuitwith signaling going to SG1. SG1 then IAM MSRN-F back to GMSC-H whichthen goes out to VMSC-F. When VMSC-F returns an ACM message back toGMSC-H it switches over to SG2 when SG1 is down in the case of fullfail-over support.

FIG. 35 is another signal flow diagram of mobile terminated calls on aMSISDN-F when the SIMM subscriber is in a FPMN and a Signal Gateway (SG)fails, under an embodiment.

In the case of partial fail-over, however, at the completion of a MAPtransaction just before the ISUP loopback at a particular SignalGateway, the data is written into the shared DB server. If the gatewaythat completed the MAP transaction failed for some reason before theISUP call, the call can be automatically handled by the remaining SignalGateway which can retrieve the call set up information (e.g. #MSRN-F,MSRN-F etc) from the shared DB server.

FIG. 36 is yet another signal flow diagram of mobile terminated calls ona MSISDN-F when the SIMM subscriber is in a FPMN and a Signal Gateway(SG) fails, under an embodiment. If Optimal Routing of voice calls isconfigured and applicable for the particular MSRN-F range, and ifbilling arrangements are made as appropriate, the Signal Gateway canchoose to return the real MSRN-F rather than #MSRN-F based on whetherthe current VLR-F is permitted for an optimally routed call. Routing ismade directly to the terminating VMSC-F from the SRI-issuingVMSC-F/GMSC-F. There will be no route to GMSC-H and no loopbacksignaling through the Signal Gateway. The Signal Gateway will generate aroaming call CDR of type (HLR interrogation HLRI) except that there isno duration, no trunking and no MSRN-2 in the CDR; an example CDRalgorithm is as follows:

Roaming call (ROAM) HLRI: ROAM_CALL_REFERENCE CallRef (MSRN-F)ROAM_EXCHANGE_ID SG ROAM_NUMBER_OF_SS_RECORDS 00 ROAM_CALLING_NUMBERCC|NDC|A (A# if known in SRI additional signal information)ROAM_CALLED_IMSI MCC|MNC|MSIN (SIMM subscriber IMSI) ROAM_CALLED_NUMBERNDC|B (SIMM MSISDN-F) ROAM_CALLED_MSRN NDC|msrn (msrn-F)ROAM_BASIC_SERVICE_TYPE 00 (tele serv.) ROAM_BASIC_SERVICE_CODE 11(telephony) ROAM_FACILITY_USAGE 00000000 ROAM_CAUSE_FOR_TERMINATION00000000 ROAM_CALL_TYPE 03 (outgoing) ROAM_ROAM_MCZ_TARIFF_CLASS MCZ(msrn-F) ROAM_ROAM_MCZ_PULSES 0000 ROAM_CALLED_MSRN_TON 05(international) ROAM_CALLED_MSRN_NPI 05 (isdn) ROAM_CALLING_NUMBER_TON05 (internat.) ROAM_CALLING_NUMBER_NPI 05 (isdn) ROAM_CALLED_NUMBER_TON05 (internat.) ROAM_CALLED_NUMBER_NPI 05 (isdn) ROAM_SRI-ISSUING-MSC:CC|NDC|msc (sri-issuing MSC-F)

FIG. 37 is yet another signal flow diagram of mobile terminated calls ona MSISDN-F when the SIMM subscriber is in a FPMN and a Signal Gateway(SG) fails, under an embodiment. MT CDR generated by VMSC-F will containIMSI and MSISDN-F. When special billing is applied, the user will becharged FPMN local airtime. In addition, the duration-less CDR generatedby the Signal Gateway will be used to add special charges for routingthe call from FPMN to HPMN and HPMN to FPMN over the leased line.

2.9.3. SIMM Subscriber in VPMN

2.9.3.1. Subscriber Called on MSISDN-H

No changes to normal GSM procedure.

2.9.3.2. Subscriber Called on MSISDN-F

Call originates from VMSC-F or reaches GMSC-F. SRI-issuing VMSC-F orGMSC-F issues a MAP SRI message to the Signal Gateway with SCCP CalledParty Address as MSISDN-F. Note that GMSC-F can either route SCCPmessages on MSISDN-F towards HPMN side via the ISC provider which isconfigured to route the CdPA=MSISDN-F towards the HPMN side, or it isconfigured in its own GTT (of STP-F/GMSC-F) to translate CdPA=MSISDN-Fto CdPA=Common-HPMN-GT-of-Signal-Gateway. The Signal Gateway transformsthis request as shown in Table 14.

TABLE 14 Message from Signal Gateway Send Routing Info from GMSC-F toGMSC-H SCCP Called Address: SCCP Called Address: GT: MSISDN-F GT:MSISDN-H SSN: 6 SSN: 6 TT: 0 TT: 0 SCCP Calling Address: SCCP CallingAddress: GT: GMSC-F GT: SG SSN: 8 SSN: 8 TT: 0 TT: 0 MAP levelparameters: MAP level parameters: MSISDN: MSISDN-F MSISDN: MSISDN-H

The request is routed to the HPMN HLR which issues a PRN request toVLR-V. The MSRN returned is routed back to the HLR and is returned inthe SRI response. The message goes via the Signal Gateway and istransformed as shown in Table 15.

TABLE 15 Message from Signal Gateway Send Routing Info Response fromHLR-H to GMSC-F via GMSC-H SCCP Called Address: SCCP Called Address: GT:SG GT: GMSC-F SSN: 8 SSN: 8 TT: 0 TT: 0 SCCP Calling Address: SCCPCalling Address: GT: HLR-H GT: SG SSN: 6 SSN: 6 TT: 0 TT: 0 MAP levelparameters: MAP level parameters: MSRN: MSRN-V MSRN: #MSRN-V

Here #MSRN-V is simply a notation that denotes a number whose mapping toMSRN-V is maintained in the Signal Gateway function. The actual numbercould just be that where the symbol ‘#’ is again a logical notation thatcan denote “#”, “999” or some prefixes. The actual number could also bethat of the pool of FPMN MSISDN-F that corresponds to the MSISDN-Fcalled. For example, if the MSISDN-F is a Beijing Mobile number, thepool should be filtered to present a Beijing Mobile number to establishthe mapping.

While reducing the use of FPMN numbers, the actual use of a prefix forthe notation #MSRN-V could be logistically challenging in cases whereevery VMSC (e.g., for calls originated in FPMN network) can issue SRIquery (e.g China Mobile) since there might be hundreds if not thousandsof VMSCs that are configured to route the call via the leased line toget the special re-routing tariff (otherwise normal IDD routing chargeswill be applied). The FPMN # pool choice on the other hand will causethe SRI-issuing VMSC (if not the GMSC-F itself, including those withoptimal routing capability) to route the call at least to the GMSC-F forthe chosen number from the pool. Only the GMSC-F then needs configuringto route the call over the leased line.

The GMSC-F is configured to route the call via the leased line to GMSC-Hbased on #MSRN-V. GMSC-H is configured to send ISUP IAM message to theSignal Gateway based on the destination number. The voice trunks areheld at GMSC-H. The Signal Gateway maps the destination number to thereal MSRN-V and routes the call back to the GMSC-H. GMSC-H routes thecall to the terminating VMSC-V.

The Signal Gateway also examines the A-party number after receiving theISUP loopback signaling from GMSC-H. If the A party number is a nationalnumber and the SRI-issuing node is a FPMN node, then the national prefixof the A party is stripped before prefixing the A party number with theinternational prefix of FPMN; otherwise the A party number is prefixeddirectly with the international prefix of FPMN. For example, assumingFPMN is China Mobile, the following modifications will be performed: ifthe first digit of the A party is 0, the first digit is stripped off andthe remaining A party number is prefixed with +86 (i.e change addressindicator to international and prefix with 86 as addressing signaldigits); if the first digit of the A party is 1, A is prefixed with +86(i.e change address indicator to international and prefix with 86 asaddressing signal digits).

FIG. 38 is a signal flow diagram of mobile terminated calls on aMSISDN-F when the SIMM subscriber is in a Visited Public Mobile Network(VPMN), under an embodiment.

The VMSC generates MT CDR and bills HPMN normal roaming rates thru TAParrangement. CDR generated by Signal Gateway will be used to bill thesubscriber for one way reroute IDD from FPMN to HPMN at a special ratesince the call is routed over the leased line. The CDR is generated asfollows:

Roaming call (ROAM): ROAM_CALL_REFERENCE CallRef (#MSRN-V)ROAM_EXCHANGE_ID SG ROAM_NUMBER_OF_SS_RECORDS 00 ROAM_CALLING_NUMBERCC|NDC|A (A#) ROAM_CALLED_IMSI MCC|MNC|MSIN (SIMM subscriber IMSI)ROAM_CALLED_NUMBER NDC|B (SIMM MSISDN-F) ROAM_CALLED_MSRN NDC|msrn(msrn-v) ROAM_IN_CIRCUIT_GROUP BSC_CCT(loopback in circuit group)ROAM_IN_CIRCUIT BSC_CCT(loopback in circuit) ROAM_OUT_CIRCUIT_GROUPTRUNK_CCT(loopback out circuit group) ROAM_OUT_CIRCUITTRUNK_CCT(loopback out circuit) ROAM_BASIC_SERVICE_TYPE 00 (tele serv.)ROAM_BASIC_SERVICE_CODE 11 (telephony) ROAM_FACILITY_USAGE 00000000ROAM_CAUSE_FOR_TERMINATION 00000000 ROAM_CALL_TYPE 03 (outgoing)ROAM_ROAM_MCZ_TARIFF_CLASS MCZ (msrn-F) ROAM_ROAM_MCZ_PULSES 0000ROAM_CALLED_MSRN_TON 05 (international) ROAM_CALLED_MSRN_NPI 05 (isdn)ROAM_CALLING_NUMBER_TON 05 (internat.) ROAM_CALLING_NUMBER_NPI 05 (isdn)ROAM_CALLED_NUMBER_TON 05 (internat.) ROAM_CALLED_NUMBER_NPI 05 (isdn)ROAM_LEG_CALL_REFERENCE CallRef G MSRN-V ROAM_CALLED_MSRN-2CC|NDC|msrn-H (#MSRN-V) ROAM_CALLED_MSRN-2_TON 05 (internat.)ROAM_CALLED_MSRN-2_NPI 05 (isdn) ROAM_SRI-ISSUING-MSC: CC|NDC|msc(sri-issuing MSC-F) ROAM_SET_UP_START_TIMEROAM_IN_CHANNEL_ALLOCATED_TIME ROAM_OUT_CHANNEL_ALLOCATED_TIMEROAM_B_IDLE_TIME ROAM_ANSWER_TIME ROAM_CHARGING_START_TIMEROAM_CHARGING_END_TIME ROAM_ROAM_MCZ_DURATION2.10. Unconditional Call Forwarding/IMSI Detached

The SIMM subscriber has the option of setting a single CFUForward-To-Number for both MSISDN-H and MSISDN-F. The FTN is returned inthe MAP SRI response.

If at the Signal Gateway function, the received FTN is the same asMSISDN-F, either the default number (e.g., voicemail) is chosen or anerror is returned to SRI query whether the call is started on MSISDN-For MSISDN-H.

This exception handling mechanism is assumed in the followingdescriptions.

2.10.1. Calls to MSISDN-H

The GMSC-H routes the call to the FTN directly without involving theSignal Gateway.

2.10.2. Calls to MSISDN-F

The SRI-issuing VMSC-F or GMSC-F issues a MAP SRI request to the SignalGateway function with SCCP Called Party Address as MSISDN-F.

Note that GMSC-F can either route SCCP messages on MSISDN-F towards HPMNside via a ISC provider which is configured to route the CdPA=MSISDN-Ftowards the HPMN side, or the GMSC-F is configured in its own GTT (ofSTP-F/GMSC-F) to translate CdPA=MSISDN-F toCdPA=Common-HPMN-GT-of-Signal-Gateway.

If the MSISDN-F subscriber is registered on FPMN, the Signal Gatewaymight perform directly a PRN query on the roamer's IMSI to VLR-F unlesssome conditions are satisfied. One of such conditions is CFU which willhave an indicator received by the Signal Gateway function from the HLR-Hduring insertSubdata from HLR-H to the Signal Gateway function.

Considering the case where the Signal Gateway cannot directly issue PRNquery to a VLR-F, the Signal Gateway function transforms the message asshown in Table 16.

TABLE 16 Message from Signal Gateway Send Routing Info from GMSC-H toGMSC-H SCCP Called Address: SCCP Called Address: GT: MSISDN-F GT:MSISDN-H SSN: 6 SSN: 6 TT: 0 TT: 0 SCCP Calling Address: SCCP CallingAddress: GT: GMSC-F GT: SG SSN: 8 SSN: 8 TT: 0 TT: 0 MAP levelparameters: MAP level parameters: MSISDN: MSISDN-F MSISDN: MSISDN-H

The GMSC-H now routes this message to the HLR in HPMN. The HLR sends theCFU FTN in the SRI response that is routed back via Signal Gateway andis modified as shown in Table 17.

TABLE 17 Message from Signal Gateway Send Routing Info Response fromHLR-H to GMSC-F via GMSC-H SCCP Called Address: SCCP Called Address: GT:SG GT: GMSC-F SSN: 8 SSN: 8 TT: 0 TT: 0 SCCP Calling Address: SCCPCalling Address: GT: HLR-H GT: SG SSN: 6 SSN: 6 TT: 0 TT: 0 MAP levelparameters: MAP level parameters: FTN: FTN FTN: #FTN

Here #FTN is simply a notation that denotes a number whose mapping toFTN is maintained in the Signal Gateway function. The actual numbercould just be that where the symbol ‘#’ is again a logical notation thatcan denote “#”, “999” or some prefixes. The actual number could also bethat of the pool of FPMN MSISDN-F that corresponds to the MSISDN-Fcalled. For example, if the MSISDN-F is a Beijing Mobile number, thepool is filtered to present a Beijing Mobile number to establish themapping. Note that the pool # assignment is only made when CFU happens,not in registration time. It is immediately freed when the call has beenforwarded.

While reducing the use of the number of FPMN numbers, the actual use ofa prefix for the notation #FTN could be logistically challenging sinceevery SRI-issuing VMSC-F (there might be hundreds if not thousands ofVMSCs) will need to be configured to route the call via the leased lineto get the special re-routing tariff (otherwise normal IDD routingcharges will be applied).

The FPMN # pool choice on the other hand will cause the SRI-issuing VMSC(if not the GMSC-F itself, including those with optimal routingcapability) to route the call at least to the GMSC-F for the chosennumber from the pool. The GMSC-F is then configured to route the callover the leased line.

Another issue with the prefixed based approach is that it might exceedboth MAP and ISUP length for a FPMN. The FPMN # pool-based approach doesnot have this issue.

The GMSC-F is configured to route the call via the leased line to GMSC-Hbased on #FTN. GMSC-H is configured to use loopback circuits to sendISUP IAM message to the Signal Gateway based on the destination number.The voice trunks are held at GMSC-H. Signal Gateway maps the destinationnumber to the real FTN and routes the call back to the GMSC-H. GMSC-Hroutes the call to FTN.

FIG. 39 is a signal flow diagram of unconditional call forwarding to aSIMM subscriber including calls to an MSISDN-F, under an embodiment.

The SIMM subscriber of an embodiment is charged for the one-way rerouteIDD (from FPMN to the Signal Gateway function) at a certain specialrate, plus the charge for the CF-Leg to FTN, based on the CDR from theSignal Gateway; an example CDR algorithm is as follows:

Forwarded Call (FORW) : FORW_CALL_REFERENCE CallRef #FTNFORW_EXCHANGE_ID SG FORW_NUMBER_OF_SS_RECORDS 01FORW_CAUSE_FOR_FORWARDING 21 (CFU) FORW_FORWARDING_IMSI MCC|MNC|MSIN(SIMM subscriber IMSI) FORW_FORWARDING_IMEI FFFF . . .FORW_FORWARDING_NUMBER NDC|B (MSISDN-F) FORW_FORWARDED_TO_IMSIMCC|MNC|MSIN (unknown by gateway) FORW_FORWARDED_TO_IMEI TAC|FAC|SN(unknown by gateway) FORW_FORWARDED_TO_NUMBER NDC|C (FTN)FORW_ORIG_CALLING_NUMBER CC|NDC|A (A#) FORW_FORWARDING_FIRST_LAC FFFFFORW_FORWARDING_FIRST_CI FFFF FORW_FORWARDING_LAST_EX_ID FFFFFORW_FORWARDING_LAST_LAC FFFF FORW_FORWARDING_LAST_CI FFFFFORW_FORWARDED_TO_FIRST_LAC FFFF FORW_FORWARDED_TO_FIRST_CI FFFFFORW_FORWARDED_TO_LAST_EX_ID FFFF FORW_FORWARDED_TO_LAST_LAC FFFFFORW_FORWARDED_TO_LAST_CI FFFF FORW_IN_CIRCUIT_GROUP BSC_CCT (loopbackin circuit group) FORW_IN_CIRCUIT BSC_CCT (loopback in circuit)FORW_OUT_CIRCUIT_GROUP BSC_CCT (loopback out circuit group)FORW_OUT_CIRCUIT BSC_CCT (loopback out circuit) FORW_BASIC_SERVICE_TYPE00 (tele serv.) FORW_BASIC_SERVICE_CODE 11 (telephony)FORW_FACILITY_USAGE 00001000 FORW_CAUSE_FOR_TERMINATION 00000000FORW_CALL_TYPE 01 (forwarded) FORW_PNI FFFFFF FORW_FORW_MCZ_TARIFF_CLASSMCZ (FTN) FORW_FORW_MCZ_PULSES 0000 FORW_FORWARDING_NUMBER_TON 05(international) FORW_FORWARDING_NUMBER_NPI 05 (isdn)FORW_FORWARDED_TO_NUMBER_TON 06 (national) FORW_FORWARDED_TO_NUMBER_NPI05 (isdn) FORW_ORIG_CALLING_NUMBER_TON 05 (internat.)FORW_ORIG_CALLING_NUMBER_NPI 05 (isdn) FORW_ORIG_CALLED_NUMBER_TON 05(international) FORW_ORIG_CALLED_NUMBER_NPI 05 (isdn)FORW_ORIG_CALLED_NUMBER NDC|B (MSISDN-F) FORW_LEG_CALL_REFERENCE CallRef#FTN FORW_FORWARDED_TO_NUMBER-2 NDC|#C (#FTN)FORW_FORWARDED_TO_NUMBER-2_TON 05 (international)FORW_FORWARDED_TO_NUMBER_NPI 05 (isdn) FORW_SRI-ISSUING_MSC: GMSC-FFORW_SET_UP_START_TIME FORW_IN_CHANNEL_ALLOCATED_TIME FORW_B_IDLE_TIMEFORW_ANSWER_TIME FORW_CHARGING_START_TIME FORW_CHARGING_END_TIMEFORW_FORW_MCZ_DURATION2.11. Conditional Call Forwarding (IMSI Attached)

If at the Signal Gateway function, the received FTN is the same asMSISDN-F, either the default number (e.g. voicemail) is chosen or anerror is returned to ISUP query regardless of whether the call isstarted on MSISDN-F or MSISDN-H.

This exception handling mechanism is assumed in the followingdescription.

2.11.1. SIMM Subscriber in HPMN

2.11.1.1. Calls to MSISDN-H

The calls to MSISDN-H are routed normally to VMSC-H without goingthrough the Signal Gateway. When a conditional call forwarding eventtriggers (CFNR, CFNRy and CFB), the VLR includes the FTN for thesenumbers and routes the call to the FTN directly. The VMSC generates CallForwarding CDR and the subscriber is billed for the CF leg.

2.11.1.2. Calls to MSISDN-F

The calls to MSISDN-F are routed by SRI-issuing VMSC-F or GMSC-F to theSignal Gateway function with SCCP Called Party Address as MSISDN-F. TheSignal Gateway function transforms the message as shown in Table 18.

TABLE 18 Message from Signal Gateway Send Routing Info from GMSC-H toGMSC-H SCCP Called Address: SCCP Called Address: GT: MSISDN-F GT:MSISDN-H SSN: 6 SSN: 6 TT: 0 TT: 0 SCCP Calling Address: SCCP CallingAddress: GT: GMSC-F GT: SG SSN: 8 SSN: 8 TT: 0 TT: 0 MAP levelparameters: MAP level parameters: MSISDN: MSISDN-F MSISDN: MSISDN-H

Consider the cases where the Signal Gateway cannot issue PRN to VLRdirectly. GMSC-H routes the request to HPMN HLR. The HLR issues a PRN toVLR-H and gets the MSRN in response which is sent back in turn in an SRIresponse to the Signal Gateway. The message is transformed as shown inTable 19.

TABLE 19 Message from Signal Gateway to Send Routing Info ResponseSRI-issuing VMSC-F or GMSC-F from HLR-H via GMSC-H SCCP Called Address:SCCP Called Address: GT: SG GT: GMSC-F SSN: 8 SSN: 8 TT: 0 TT: 0 SCCPCalling Address: SCCP Calling Address: GT: HLR-H GT: SG SSN: 6 SSN: 6TT: 0 TT: 0 MAP level parameters: MAP level parameters: MSRN: MSRN-HMSRN: #MSMN-H

Note that #MSRN-H is just a number that represents a mapping to theMSRN-H as explained before. The SRI-issuing VMSC-F or GMSC-F routes theISUP IAM message via the leased line to the Signal Gateway. The loopbackcircuit is used with signaling going through the Signal Gateway. TheSignal Gateway maps #MSRN-H to MSRN-H and loops back the signal atGMSC-H. Call is routed to VMSC-H.

Upon the triggering of a Late Call Forwarding event (CFB, CFNR, CFNRy),the VMSC-H routes the call to the corresponding FTN number, if any.

The CDR generated at the Signal Gateway is no different from a normalroaming call CDR, but is not so limited.

2.11.2. SIMM Subscriber in FPMN

When a SIMM subscriber registers at HPMN or VPMN, the real FTN values ofthe subscriber will be stored in the VLR. However during the locationupdate for the SIMM subscriber at FPMN, the Signal Gateway can changethe FTN value based on the FTN value, subscriber's FTN flag and SIMMsubscriber's current location (VLR-F) and the subscriber's MSISDN-F. TheFTN value will not be substituted by the Signal Gateway when issuinginsertSubData to a FPMN VLR-F for a SIMM subscriber with MSISDN-F if theVLR-F network, FTN network, and MSISDN-F network has a correspondingentry in the following table maintained by HPMN or the subscriber'sFTN-no-change flag is set. In this case, late call forwarding will bedirectly routed to FTN without going through the Signal Gateway. Table20 shows FTN-no-change-at-FPMN.

TABLE 20 MSISDN-F network range VLR-F network range FTN network range

For example, the entry could be for all FPMN networks, e.g. ChinaMobile. Then as long as FTN is a China Mobile number, it will not bechanged by the Signal Gateway. Another example could be that onlyprovincial networks have the entries in the table. Then if the BeijingMSISDN-F is used by the SIMM in a Beijing VLR-F but the FTN is a GuangDong Mobile number, the FTN will be replaced by the Signal Gateway. Theexact network entry in the table depends on the billing arrangement HPMNwith FPMN (and provincial FPMNs).

Following is a description of the case where the FTN has been changed.In this case, the forwarding call is routed back to the Signal Gatewaywhich can then generate the CDR for billing purposes.

2.11.2.1. Calls to MSISDN-H

The GMSC-H issues an SRI request to HPMN HLR with SCCP Called PartyAddress as MSISDN-H. The HLR issues a PRN to the Signal Gateway sincethe Update Location was routed via it. The PRN message is transformed asshown in Table 21.

TABLE 21 Message from Signal Gateway Provide Roaming Number from HLR-Hto VLR-F via GMSC-H SCCP Called Address: SCCP Called Address: GT: SG GT:VLR-F SSN: 7 SSN: 7 TT: 0 TT: 0 SCCP Calling Address: SCCP CallingAddress: GT: HLR-H GT: SG SSN: 6 SSN: 6 TT: 0 TT: 0 MAP Parameters: MAPParameters: MSISDN: MSISDN-H MSISDN: MSISDN-F

The PRN response is also routed back to the HPMN HLR via the SignalGateway. The message is transformed as shown in Table 22.

TABLE 22 Provide Roaming Number Response Message from Signal Gatewayfrom VLR-F to HLR-H via GMSC-H SCCP Called Address: SCCP Called Address:GT: SG GT: HLR-H SSN: 6 SSN: 6 TT: 0 TT: 0 SCCP Calling Address: SCCPCalling Address: GT: VLR-F GT: SG SSN: 7 SSN: 7 TT: 0 TT: 0 MAP levelparameters: MAP level parameters: MSRN: MSRN-F MSRN: #MSRN-F

Again, #MSRN-F is just a notation that represents a number that maps toMSRN-F in the Signal Gateway function. GMSC-H routes the call throughthe loopback circuits with signaling going through the Signal Gateway.Signal Gateway maps #MSRN-F to MSRN-F and loops back the signaling withthe voice ports established at GMSC-H. GMSC-H routes the call over theleased line. Note that the routing criterion is such that all calls fromGMSC-H to an FPMN number are routed over the leased line to the GMSC-Fthat corresponds to the FPMN number.

If the RCM flag is on for the subscriber, the Signal Gateway willgenerate a new prefixed MSRN number, for example $MSRN, and it sets thegeneric number field to MSISDN-H where the number qualifier indicator isset to additional called number in the IAM message. The Signal Gatewaythen routes the call through the GMSC-H which recognizes it as intendedfor the CSL service node for HK ringback tone for voicemail optimizedlate call forwarding.

In order to detect and handle Late Call Forwarding, care is taken tomake sure that only one Unanswered Call is in progress at any point intime; otherwise the Signal Gateway might not be able to determine whichincoming leg is to be connected with the actual FTN when LCF eventtriggers. To achieve this, a call state is maintained for eachsubscriber roaming in FPMN when a call has been routed through to theFPMN side. There is also a flag in the call state that indicates if thecall has been handled (connected or forwarded, etc.) or not.

When a new call is routed through the Signal Gateway for the samesubscriber, if such a state exists and the flag is set, the call isimmediately forwarded based on the CFB condition unless optimal routingtakes place. The flag is cleared when the call is connected or releasedor LCF event is handled. In this way, call waiting and conferencecalling in LCF can be supported by the Signal Gateway. If the SRI or PRNrequest is received at the Signal gateway when the flag is set and thesubscriber is registered at FPMN, then: (1) if it is the MSISDN-F of theSIMM subscriber that gets called, then (a) if the optimal routing is notallowed, the request will not be returned with a new #MSRN (no MSRN willbe requested by the Signal gateway), instead early call forwarding willbe triggered with ECF value if it is not empty or with the CFB value ifthe ECF value is empty; or (b) if optimal routing is allowed, then #MSRNwill be assigned; or (2) if it is the MSISDN-H of the SIMM subscribergets called, the request will not be returned with a new #MSRN (no MSRNwill be requested by the Signal gateway), instead early call forwardingwill be triggered with ECF value if it is not empty or with the CFBvalue if the ECF value is empty. In both cases, the default CF value canalso be used in place of the ECF value (whether it is empty or not).

If the subscriber is registered at FPMN and the optimal routing is notallowed, the request will not be returned with a new #MSRN (no MSRN willbe requested by the Signal Gateway), instead early call forwarding willbe triggered with ECF value if it is not empty or with the CFB value ifthe ECF value is empty.

The call state is copied to the shared memory of the DB server. In theevent of failure of the chosen Signal Gateway in the set up of the ISUPloopback call, the other gateway takes over the signaling. The callstate also includes periodic (e.g., configurable X seconds) durationupdate. When the call is released, the call state is cleared after it isused to build CDR in the database.

FIG. 40 is a signal flow diagram of conditional call forwarding to aSIMM subscriber in an FPMN including calls to an MSISDN-H, under anembodiment.

There are two ways of implementing #FTN representation, depending onFPMN switch capabilities. The first is to assign a different #FTN from apool to each FTN value for each subscriber. This is switch independent,but would possible include a large number of #FTNs from either FPMN orHPMN. The second is to assign a different #FTN for each conditionforwarding type. These depend on the OCN/ODN support of both the FPMNand HPMN.

Regarding the first implementation in which one FTN is used for each LCFvalue for each subscriber, the Signal Gateway creates a mapping betweenthe allocated MSISDN (#FTN) from a pool and the actual FTN. SG managesthis mapping as follows: (a) SG deletes this mapping and frees theMSISDN whenever it gets Cancel Location from HLR for the VLR and when itgets another Insert Subscriber Data, either standalone or as part ofupdate location transaction which removes the call forwarding; (b) Incase the call forwarding is changed to a different number, InsertSubscriber Data is issued by HLR and in that case SG changes themapping. If Insert Subscriber Data has the same FTN as before, themapping maintained in Signal Gateway is not changed. Otherwise, themapping will be to the new FTN in the Insert Subscriber Data messagewith the same #FTN as before; and (c) There are two ways of creating thepool of FTN #s. One is to populate the pool with home MSISDN-H numbers;the other is to populate the pool with FPMN MSISDN-F numbers. The formerhas the advantage that it is less resource stressful to FPMN. Howeverevery GMSC (e.g., Beijing GMSC) in FPMN will be configured to route thecall to the GMSC-F (e.g., Guang Dong GMSC) that has the leased line toGMSC-H. The second has the advantage that LCF calls are guarantee to berouted to GMSC-F without any configuration on their GMSCs. Only GMSC-Fthat has the leased line connection will be configured to route the callon #FTN over the leased line.

Note that the pool of #FTNs is shared not split by SG1 and SG2. Besides,it is assumed MSC will route all ISUP and SCCP with callednumber=dedicated range of MSISDN-F and #FTN to SG1/SG2.

The system of an embodiment does not send any ISUP or SCCP message withcalled number=same range of MSISDN-F or #FTN back to MSC.

Note also that care is taken to ensure that only one Unanswered Call isin progress at any point in time; otherwise the Signal Gateway may notbe able to determine which incoming leg is to be connected with theactual FTN when LCF event triggers.

Regarding the second implementation in which one FTN is assigned foreach LCF Condition type, when the Insert Subscriber Data is routed viathe Signal Gateway, the gateway maintains a mapping between MSISDN-F,MSISDN-H and FTN values for CFB, CFNR and CFNRy. Table 23 is acall-forwarding table.

TABLE 23 MSISDN-F Call forwarding Call forwarding MSISDN-H type value

It then substitutes the original FTN values with the corresponding valuefor each Call Forwarding event type in the translated Insert SubscriberData message sent to VLR-F. When LCF event triggers at VMSC-F, VMSC-Flooks up the FTN information from VLR-F and routes the call to thecorresponding number. Note that the calls are routed to a common numberfor each type of condition forwarding and GMSC-H is configured to sendthe calls using loopback circuits with signaling through the SignalGateway. The Signal Gateway function extracts the OCN or ODN value fromthe ISUP IAM, and extracts the LCF event type based on the number towhich the call was forwarded. It then releases the current forwarded legB (and C) of the call while maintaining the A-leg of the call. Theoriginal call leg (A) is then forwarded to the FTN number (D leg)retrieved by looking up the OCN/ODN values within the databasecontaining original FTN numbers. This achieves optimal routing ofLate-Call-Forwarding. It also generates a CF CDR. This approach does notrequire reserving a pool of MSISDN numbers from HPMN or FPMN.

FIG. 41 is another signal flow diagram of conditional call forwarding toa SIMM subscriber in an FPMN including calls to an MSISDN-H, under anembodiment.

The second implementation above in which one FTN is assigned for eachLCF Condition type is recommended if OCN/ODN is supported by both HPMNand FPMN. Unlike the CFU case where #FTN is only assigned from a poolwhen CFU happens not at registration time, the first implementationwould require such an assignment from a pool at registration timewhether LCF is triggered or not.

Each FPMN will be configured to apply one of the two implementations inLCF. For example, one service provider can be configured to have the OCNimplementation; while another service provider can have the poolimplementation.

An example algorithm supporting conditional call forwarding when theSIMM subscriber is in the HPMN and called on the MISIDN-H is as follows:

Forwarded Call (FORW): FORW_CALL_REFERENCE CallRef MSISDN-HFORW_EXCHANGE_ID SG FORW_NUMBER_OF_SS_RECORDS 01FORW_CAUSE_FOR_FORWARDING 29 (CFB) FORW_FORWARDING_IMSI MCC|MNC|MSIN(SIMM subscriber IMSI) FORW_FORWARDING_IMEI FFFF . . .FORW_FORWARDING_NUMBER NDC|B (MSISDN-H) FORW_FORWARDED_TO_IMSIMCC|MNC|MSIN (unknown by gateway) FORW_FORWARDED_TO_IMEI TAC|FAC|SN(unknown by gateway) FORW_FORWARDED_TO_NUMBER NDC|C (FTN)FORW_ORIG_CALLING_NUMBER CC|NDC|A (A#) FORW_FORWARDING_FIRST_LAC FFFFFORW_FORWARDING_FIRST_CI FFFF FORW_FORWARDING_LAST_EX_ID FFFFFORW_FORWARDING_LAST_LAC FFFF FORW_FORWARDING_LAST_CI FFFFFORW_FORWARDED_TO_FIRST_LAC FFFF FORW_FORWARDED_TO_FIRST_CI FFFFFORW_FORWARDED_TO_LAST_EX_ID FFFF FORW_FORWARDED_TO_LAST_LAC FFFFFORW_FORWARDED_TO_LAST_CI FFFF FORW_IN_CIRCUIT_GROUP BSC_CCT (loopbackin circuit group) FORW_IN_CIRCUIT BSC_CCT (loopback in circuit)FORW_OUT_CIRCUIT_GROUP BSC_CCT (loopback out circuit group)FORW_OUT_CIRCUIT BSC_CCT (loopback out circuit) FORW_BASIC_SERVICE_TYPE00 (tele serv.) FORW_BASIC_SERVICE_CODE 11 (telephony)FORW_FACILITY_USAGE 00001000 FORW_CAUSE_FOR_TERMINATION 00000000FORW_CALL_TYPE 01 (forwarded) FORW_PNI FFFFFF FORW_FORW_MCZ_TARIFF_CLASSMCZ (FTN) FORW_FORW_MCZ_PULSES 0000 FORW_FORWARDING_NUMBER_TON 06(national) FORW_FORWARDING_NUMBER_NPI 05 (isdn)FORW_FORWARDED_TO_NUMBER_TON 06 (national) FORW_FORWARDED_TO_NUMBER_NPI05 (isdn) FORW_ORIG_CALLING_NUMBER_TON 06 (nat.)FORW_ORIG_CALLING_NUMBER_NPI 05 (isdn) FORW_ORIG_CALLED_NUMBER_TON 06(national) FORW_ORIG_CALLED_NUMBER_NPI 05 (isdn) FORW_ORIG_CALLED_NUMBERNDC|B (MSISDN-H) FORW_LEG_CALL_REFERENCE CallRef FTNFORW_SRI-ISSUING_MSC: GMSC-H FORW_SET_UP_START_TIMEFORW_IN_CHANNEL_ALLOCATED_TIME FORW_B_IDLE_TIME FORW_ANSWER_TIMEFORW_CHARGING_START_TIME FORW_CHARGING_END_TIME FORW_FORW_MCZ_DURATION2.11.2.2. Calls to MSISDN-F

When the user is called on MSISDN-F, the SRI-issuing VMSC-F or GMSC-Fissues a SRI request to the Signal Gateway with SCCP Called PartyAddress as MSISDN-F. The Signal Gateway modifies the SRI message asshown in Table 24.

TABLE 24 Message from Signal Gateway Send Routing Info from GMSC-F toGMSC-H SCCP Called Address: SCCP Called Address: GT: MSISDN-F GT:MSISDN-H SSN: 6 SSN: 6 TT: 0 TT: 0 SCCP Calling Address: SCCP CallingAddress: GT: GMSC-F GT: GMSC-F SSN: 8 SSN: 8 TT: 0 TT: 0 MAP levelparameters: MAP level parameters: MSISDN: MSISDN-F MSISDN: MSISDN-H

The HLR issues a PRN request that is also routed via the Signal Gatewayand is transformed as shown in Table 25.

TABLE 25 Message from Signal Gateway Provide Roaming Number from HLR-Hto VLR-F via GMSC-H SCCP Called Address: SCCP Called Address: GT: F-SGGT: VLR-F SSN: 7 SSN: 7 TT: 0 TT: 0 SCCP Calling Address: SCCP CallingAddress: GT: HLR-H GT: SG SSN: 6 SSN: 6 TT: 0 TT: 0 MAP levelparameters: MAP level parameters: MSC address: SG MSC address: VMSC-FMSISDN: MSISDN-H MSISDN: MSISDN-F

Note that MSISDN is an optional parameter and if present, it is replacedwith MSISDN-F. The Signal Gateway also transforms the PRN response asshown in Table 26.

TABLE 26 Provide Roaming Number Response Message from Signal Gatewayfrom VMSC-F to HLR-H via GMSC-H SCCP Called Address: SCCP CalledAddress: GT: SG GT: HLR-H SSN: 6 SSN: 6 TT: 0 TT: 0 SCCP CallingAddress: SCCP Calling Address: GT: VLR-F GT: F-SG SSN: 7 SSN: 7 TT: 0TT: 0 MAP level parameters: MAP level parameters: MSRN: MSRN-F MSRN:#MSRN-F

Since the roamer information (IMSI, VMSC-F, VLR-F, etc.) is maintainedwhen the subscriber is in FPMN, the Signal Gateway can also directlyissue PRN to the VLR-F to obtain the roaming number.

The #MSRN number is returned as SRI response to GMSC-F or theSRI-issuing VMSC-F. The SRI-issuing VMSC-F or GMSC-F routes the call to#MSRN-F over the leased line to GMSC-H. The GMSC-H sets up the call withloopback circuits with signaling going through the Signal Gatewayfunction. The Signal Gateway instructs GMSC-H to set up the call on thereal MSRN-F.

When the LCF event triggers, VMSC-F forwards the call to the FTN sent aspart of the Insert Subscriber Data message. The call flow is similar tothe call on MSISDN-H as described above.

FIG. 42 is signal flow diagram of conditional call forwarding to a SIMMsubscriber in an FPMN including calls to an MSISDN-F, under anembodiment.

An example algorithm supporting conditional call forwarding when theSIMM subscriber is in the HPMN and called on the MISIDN-F is as follows:

Forwarded Call (FORW): FORW_CALL_REFERENCE CallRef MSISDN-FFORW_EXCHANGE_ID SG FORW_NUMBER_OF_SS_RECORDS 01FORW_CAUSE_FOR_FORWARDING 29 (CFB) FORW_FORWARDING_IMSI MCC|MNC|MSIN(SIMM subscriber IMSI) FORW_FORWARDING_IMEI FFFF . . .FORW_FORWARDING_NUMBER NDC|B (MSISDN-F) FORW_FORWARDED_TO_IMSIMCC|MNC|MSIN (unknown by gateway) FORW_FORWARDED_TO_IMEI TAC|FAC|SN(unknown by gateway) FORW_FORWARDED_TO_NUMBER NDC|C (FTN)FORW_ORIG_CALLING_NUMBER CC|NDC|A (A#) FORW_FORWARDING_FIRST_LAC FFFFFORW_FORWARDING_FIRST_CI FFFF FORW_FORWARDING_LAST_EX_ID FFFFFORW_FORWARDING_LAST_LAC FFFF FORW_FORWARDING_LAST_CI FFFFFORW_FORWARDED_TO_FIRST_LAC FFFF FORW_FORWARDED_TO_FIRST_CI FFFFFORW_FORWARDED_TO_LAST_EX_ID FFFF FORW_FORWARDED_TO_LAST_LAC FFFFFORW_FORWARDED_TO_LAST_CI FFFF FORW_IN_CIRCUIT_GROUP BSC_CCT (loopbackin circuit group) FORW_IN_CIRCUIT BSC_CCT (loopback in circuit)FORW_OUT_CIRCUIT_GROUP BSC_CCT (loopback out circuit group)FORW_OUT_CIRCUIT BSC_CCT (loopback out circuit) FORW_BASIC_SERVICE_TYPE00 (tele serv.) FORW_BASIC_SERVICE_CODE 11 (telephony)FORW_FACILITY_USAGE 00001000 FORW_CAUSE_FOR_TERMINATION 00000000FORW_CALL_TYPE 01 (forwarded) FORW_PNI FFFFFF FORW_FORW_MCZ_TARIFF_CLASSMCZ (FTN) FORW_FORW_MCZ_PULSES 0000 FORW_FORWARDING_NUMBER_TON 05(international) FORW_FORWARDING_NUMBER_NPI 05 (isdn)FORW_FORWARDED_TO_NUMBER_TON 06 (national) FORW_FORWARDED_TO_NUMBER_NPI05 (isdn) FORW_ORIG_CALLING_NUMBER_TON 02 (internat.)FORW_ORIG_CALLING_NUMBER_NPI 05 (isdn) FORW_ORIG_CALLED_NUMBER_TON 05(international) FORW_ORIG_CALLED_NUMBER_NPI 05 (isdn)FORW_ORIG_CALLED_NUMBER NDC|B (MSISDN-F) FORW_LEG_CALL_REFERENCE CallRefFTN FORW_SRI-ISSUING_MSC: GMSC-F FORW_SET_UP_START_TIMEFORW_IN_CHANNEL_ALLOCATED_TIME FORW_B_IDLE_TIME FORW_ANSWER_TIMEFORW_CHARGING_START_TIME FORW_CHARGING_END_TIME FORW_FORW_MCZ_DURATION2.11.3. SIMM Subscriber in VPMN2.11.3.1. Calls to MSISDN-H

The GSM procedures apply.

2.11.3.2. Calls to MSISDN-F

The GMSC-F is configured to issue a SRI to the Signal Gateway with SCCPCalled Party Address as MSISDN-F. Note that GMSC-F can either route SCCPmessages on MSISDN-F towards HPMN side via a ISC provider which isconfigured to route the CdPA=MSISDN-F towards the HPMN side or it isconfigured in its own GTT (of STP-F/GMSC-F) to translate CdPA=MSISDN-Fto CdPA=Common-HPMN-GT-of-Signal-Gateway. The Signal Gateway modifiesthe message as shown in Table 27.

TABLE 27 Message from Signal Gateway Send Routing Info from GMSC-H toGMSC-H SCCP Called Address: SCCP Called Address: GT: MSISDN-F GT:MSISDN-H SSN: 6 SSN: 6 TT: 0 TT: 0 SCCP Calling Address: SCCP CallingAddress: GT: GMSC-F GT: SG SSN: 8 SSN: 8 TT: 0 TT: 0 MAP levelparameters: MAP level parameters: MSISDN: MSISDN-F MSISDN: MSISDN-H

The HPMN HLR issues a PRN to the VLR-V and receives an MSRN in turn. TheMSRN is returned in the SRI response and the Signal Gateway transformsit as shown in Table 28.

TABLE 28 Message from Signal Gateway Send Routing Info Response fromHLR-H to GMSC-F via GMSC-H SCCP Called Address: SCCP Called Address: GT:SG GT: GMSC-F SSN: 8 SSN: 8 TT: 0 TT: 0 SCCP Calling Address: SCCPcalling Address: GT: HLR-H GT: SG SSN: 6 SSN: 6 TT: 0 TT: 0 MAP levelparameters: MAP level parameters: MSRN: MSRN-V MSRN: #MSRN-V

The GMSC-F routes the call via the leased line (by looking at the#MSRN-V) to the Signal Gateway. The Signal Gateway maps the #MSRN-V tothe real MSRN-V and routes the call back to GMSC-H with MSRN-V as thedestination number. The call is terminated on VMSC-V.

When the LCF event triggers, VMSC-V directly routes the call to the FTNnumbers received in the Insert Subscriber Data message.

FIG. 43 is a signal flow diagram of conditional call forwarding to aSIMM subscriber in a VPMN including calls to an MSISDN-F, under anembodiment.

The CDR will be no different from a roaming call on MSISDN-F of a SIMMsubscriber where the SIMM subscriber is registered at a VPMN network.

2.12. Support for Optimal Routing

The SIMM System/Service of an embodiment includes Optimal RoutingSupport for voice routing when the Calling and Called party/forward-toparty are in the same country. Several cases of optimal routing aredescribed below.

One embodiment of optimal routing is when the MSISDN-F is called whenthe subscriber is not at the HPMN (i.e., the subscriber is at FPMN orVPMN). FIG. 44 is a signal flow diagram of call routing when an MSISDN-Fis called and the subscriber is not in the HPMN, under an embodiment. Inthis case, the Signal Gateway function addresses the optimal routing onMSRN and ECF/CFU forward-to number by maintaining a table of OR-allowedrecords each contains a MSISDN-F number, a GMSC-F or SRI-issuing VMSC-Fnumber, and a destination number which can be MSRN, FTN, VMSC numbers.The value of each field can be a range or a prefix. If the call onMSISDN-F is to be routed from the GMSC-F/VMSC-F to a MSRN/FTN that issatisfied by a record in the FPMN-OR-allowed table, then the call can beoptimally routed. If the call is OR routable, then the Signal Gatewayfunction will return the MSRN/FTN directly to the SRI-issuingVMSC-F/GMSC-F. The Signal Gateway will not be able to generate aduration CDR in both cases although the MAP transaction record isgenerated. Table 29 shows FPMN-OR-allowed.

TABLE 29 MSISDN-F SRI-issuing MSC-F Destination #

Note that the FPMN-OR-allowed table can allow an OR call for a SIMMsubscriber in one part of FPMN network and disallow an OR call inanother part when MSISDN-F is called even though the caller is on thesame FPMN switch in both cases. For example, a SIMM subscriber with aBeijing Mobile number is registered in a Beijing network. A calloriginated from a Beijing network could be optimally routed to thesubscriber because the OR-allowed table allows such a case. The sameSIMM subscriber with a Beijing Mobile number is later registered in aShanghai network. A call originated from a Beijing network might not beoptimally routed to the subscriber since the OR-allowed table does nothave a supporting record.

It is also possible that the SRI-issuing MSC on MSISDN-F is not allowedfor optimal routing to a VMSC-F/MSRN but the GMSC-F for MSISDN-F isallowed for optimal routing. In this case, the Signal Gateway can returnthe original MSISDN back to the SRI-issuing MSC which can then route thecall nationally to GMSC-F which can then issue SRI on MSISDN-F to theSignal Gateway function. The Signal Gateway function can then obtainMSRN/FTN and return it directly to the GMSC-F which can then optimallyroute the call to the destination MSRN or FTN.

FIG. 45 is another signal flow diagram of call routing when an MSISDN-Fis called and the subscriber is not in the HPMN, under an embodiment. Inthis example, a Beijing Mobile caller calls the SIMM subscriber's GMCCnumber when the caller is in Beijing and the subscriber is registered atGuang Dong, even though a direct optimal routing is not allowed, it ispossible to route the call to Guang Dong first. Afterwards; the GMSC-Fat GMCC can route the call to the VMSC-F at Beijing rather than routingthe call through GMSC-H with loopback signaling through the SignalGateway.

Another example is when the SIMM subscriber goes to a third VPMN; if hisMSISDN-F is called, the call will reach GMSC-F first. If OR is allowed,the call will be routed directly from GMSC-F to VPMN; otherwise the callwill be routed thru HPMN which will then route the call to VPMN.

If OR routing is allowed, the Signal Gateway will not be able togenerate duration CDR although MAP signaling CDR can still be generated.To OR or not is controlled by the OR table. Billing arrangement need bemade between HPMN and FPMN in both cases.

Optimal routing for a SIMM subscriber called via the MSISDN-F when thesubscriber is registered at an FPMN is acceptable since there is aspecial relationship between FPMN and HPMN.

When a SIMM subscriber is called via the MSISDN-F when the subscriber isregistered at an VPMN network, non-optimal routing will involve an IDDroute from FPMN to HPMN and then another IDD route from HPMN to VPMN.The advantage to this is that since VPMN always presents the MT-TAP toHPMN based on IMSI, HPMN can then top it up with IDD leg to VPMN rightaway to charge the subscriber while eating the cost of the IDD leg fromFPMN to HPMN since the leg can be a direct link from FPMN to HPMN. Evenif the HPMN operator wants to charge the IDD leg from FPMN to HPMN,because the Signal Gateway has the CDR, HPMN can reconcile the MT-TAPfrom VPMN with the Signal Gateway CDR for those MT-TAP records on theSIMM IMSI range. This leg on the direct link can be charged cheaper thana normal route from FPMN to HPMN. The subscriber pays two legs of IDDrather than one leg or a local leg (if at FPMN) under this scenario.

However when optimal routing takes place, since VPMN still presents theMT-TAP records to HPMN, the FPMN and HPMN rely on each other's CDR forcorrect billing. HPMN cannot just top up the IDD leg from HPMN to VPMNto charge the subscriber. It needs to examine the MT-TAP on SIMM IMSIseparately from ordinary MT-TAP records. It needs to be reconciled withthe MAP transaction records in the Signal Gateway. The map transactionrecord will also indicate which MSISDN-F is called so correct IDD legtop up can be applied. However because MAP transaction does not haveduration, reconciliation need be careful about the timing.Alternatively, HPMN can wait for FPMN to send out the rerouted CDR onMSISFN-F which will have durations to do the final reconciliation.

Another embodiment of optimal routing is when an HPMN network user(local or roamer) calls MSISDN-F of a SIMM subscriber when thesubscriber is not on the FPMN network. FIG. 46 is a signal flow diagramof call routing when an HPMN user (local or roamer) calls an MSISDN-F ofa SIMM subscriber and the subscriber is not in the FPMN, under anembodiment.

In this embodiment, the GMSC-H is configured to issue SRI-query on theMSISDN-F to the Signal Gateway. The Signal Gateway function maintains alist of MSISDN-Fs that are allowed (e.g. may be offered as asubscription) to OR route the call for the case.

When an SRI query is received at a Signal Gateway, the gateway checks ifthe SRI-issuing GT is an HPMN one and, if it is, it checks the MSISDN-Fin the query against the HPMN-OR-allowed table. If there is a match, thereal MSRN/FTN (after finding it) is returned; otherwise the originalMSISDN-F is returned.

FIG. 47 is another signal flow diagram of call routing when an HPMN user(local or roamer) calls an MSISDN-F of a SIMM subscriber and thesubscriber is not in the FPMN, under an embodiment. Table 30 showsHPMN-OR-allowed.

TABLE 30 MSISDN-F

Note that the SIMM subscribers can get OR calls from either a local or aroamer in HPMN. The SIMM receiving party might be charged a subscriptionfee or a markup for reduced phone rate due to optimal routing.

While the Signal Gateway will have a SRI query record, the SignalGateway will not be able to generate the CDR. However this service caneither be offered as a subscription service or a one time fixed charge,then the SRI query record will be sufficient. The MTC record for theSIMM subscriber that received such an OR-routed call will be as ifhis/her HPMN number had been called.

The above simple HPMN-OR-allowed table can be further extended to covermore fine-grained cases where destination # can be FTN, MSRN, VMSC/VLR #ranges.

Table 31 shows HPMN-OR-allowed.

TABLE 31 MSISDN-F SRI-issuing MSC-H Destination #

However if destination # is FPMN, ISUP loopback will be used as if thesubscriber's MSISDN-H is called when the subscriber is registered atFPMN even OR is allowed.

FIG. 48 is yet another signal flow diagram of call routing when an HPMNuser (local or roamer) calls an MSISDN-F of a SIMM subscriber and thesubscriber is not in the FPMN, under an embodiment. Similar CFU/ECFforwarding can also be optimally addressed when the FTN is a FPMNnumber.

FIG. 49 is still another signal flow diagram of call routing when anHPMN user (local or roamer) calls an MSISDN-F of a SIMM subscriber andthe subscriber is not in the FPMN, under an embodiment.

The Signal Gateway produces CDR similar to the case as if thesubscriber's MSISDN-H is called when the subscriber is registered atFPMN except that the CDR indicates it is the MSISDN-F that is originallycalled. In this way, HPMN can choose to charge a mark-up if so desired.

2.13. Determine Number Called On

In general, it is not always possible to determine which number(MSISDN-H or MSISDN-F1 to MSISDN-Fn) a SIMM subscriber is called on.However, if caller ID is delivered to the SIMM subscriber, withoutoptimal routing (when the SIMM subscriber is at VPMN), the subscribercan determine which number has been called via the caller ID. Inpractice, caller ID is usually delivered between HPMN and FPMNcountries. Some operators also deliver caller ID to outbound roamers.

When MSISDN-H is called while the SIMM subscriber is at HPMN or VPMN, nocaller ID will be changed. The subscriber can deduce that his MSISDN-His called.

When MSISDN-H is called while the SIMM subscriber is at FPMN-i (where iis 1, 2, . . . n), since the call will always go thru the Signal Gatewayvia ISUP loopback or IN, the Signal Gateway will modify the callingparty A to A^ if the caller ID is also a MSISDN-F-i number and will notchange the calling party A otherwise. Here A^ is a logical notation thatcontains A along with some other notation that denotes the HPMN numbereither as a prefix or postfix. The exact form of A^ will depend onoperator requirements. Some examples of A^ include A99, A#, A*, ##-A,99-A. Postfix has the advantage that the number can be immediatelycalled. Prefix has the advantage that caller name from phone book can bedisplayed.

When MSISDN-F-i is called while the SIMM subscriber is at HPMN or XPMN,then the call will always go thru the Signal Gateway via ISUP loopbackor IN without optimal routing. In this case, the Signal Gateway willmodify the calling party A to A′ where A′ is a logical notation thatcontains A along with some other notation that denotes the FPMN numbereither as a prefix or postfix. The exact form of A's will depend onoperator requirements. Some examples of A′ could be A00i, A*i, A#i,#i-A, and 00i-A. Postfix has the advantage that the number can beimmediately called. Prefix has the advantage that caller name from phonebook can be displayed.

When optimal routing is allowed at VPMN, however since the call is notgoing thru the signal relay gateway, caller ID cannot be manipulated tolet the SIMM recipient to deduce which number is called on. This is oneof the disadvantages of allowing optimal routing to VPMN network fromFPMN when calls are made on MSISDN-F when the SIMM roamer is at VPMN.

When optimal routing is allowed at FPMN, since caller ID is shown, eventhough it is not going thru the Signal Gateway, the SIMM roamer at FPMNcan deduce that the call is on his MSISDN-F of the FPMN in which he/sheis located.

Alternatively, for MT calls (MSISDN-F or MSISDN-H) to SIMM subscribersgoing thru the Signal Gateway, an out-of-band SMS/USSD over SS7 will besent to the subscriber handset with the message “Called on MSISDN-F” ifnot called on MSISDN-H. If the number is called on MSISDN-H, no messagewill be sent to the handset.

2.14. Mobile Terminated SMS

The SIMM subscriber of an embodiment is able to receive SMS in any GSMnetwork irrespective of it being sent to MSISDN-H or MSISDN-F. The SMScould be sent from any SMSC.

2.14.1. SMS to MSISDN-H when Subscriber in HPMN

Normal GSM operations apply regardless of whether the SMS is sent bySMSC-H, SMSC-F or SMSC-V. VMSC-H MT SMS CDR is used for SMSInter-working settlements between HPMN and APMN.

2.14.2. SMS to MSISDN-H when Subscriber in FPMN

Only when the SIMM subscriber registers at FPMN and the VMSC/SGSNaddress is modified to a Signal Gateway GT is the Signal Gatewayfunction involved. To VLR-F, the Signal Gateway is the HLR for thesubscriber and it also knows the VMSC-F of the subscriber. SMSC-X(SMSC-H, SMSC-F or SMSC-V) issues an SRI-SM to the HLR-H. HLR-H has theaddress of the Signal Gateway as the serving MSC and returns it inSRI-SM response. SMSC-X issues a FSM to the Signal Gateway. The SignalGateway performs the translation as shown in Table 32.

TABLE 32 Message from Signal Gateway MT FSM from SMSC-X to VMSC-F viaGMSC-H SCCP Called Address: SCCP Called Address: GT: SG GT: VMSC-F SSN:8 SSN: 8 TT: 0 TT: 0 SCCP Calling Address: SCCP Calling Address: GT:SMSC-X GT: SG SSN: 8 SSN: 8 TT: 0 TT: 0

The Sending SMSC address, the Sender address and the recipient addressin the MAP message are left unchanged. Note that the recipient addressSP-RP-DA is based on IMSI-H (or LMSI), there is no need to worry aboutswapping MSISDN-H by MSISDN-F.

Note that the SCCP Calling Address has also been changed and hence theresponse also goes through the Signal Gateway as shown in Table 33.

TABLE 33 Message from Signal Gateway MT FSM Response from VMSC-F toSMSC-X via GMSC-H SCCP Called Address: SCCP Called Address: GT: SG GT:SMSC-X SSN: 8 SSN: 8 TT: 0 TT: 0 SCCP Calling Address: SCCP CallingAddress: GT: VMSC-F GT: SG SSN: 8 SSN: 8 TT: 0 TT: 0

FIG. 50 is a signal flow diagram for a mobile terminated Short MessageService (SMS) message to an MSISDN-H when the subscriber is in an FPMN,under an embodiment.

The Signal Gateway generates a CDR for this transaction and can be usedto apply special charges/discounts. The VMSC-F MT SMS CDR is used forSMS Inter-working settlement. Special rates may be negotiated for thespecific HPMN IMSI range for Multiple MSISDN subscriber. An example CDRalgorithm is as follows:

SMMT CDR SMMT_CALL_REFERENCE SMMT_EXCHANGE_ID SG SMMT_CALLED_IMSI SIMMsubscriber IMSI SMMT_CALLED_IMEI FFFF . . . SMMT_CALLED_NUMBER NDC|B(MSISDN-H) SMMT_CALLED_NUMBER_TON 06 (national) SMMT_CALLED_SUBS_LACFFFF SMMT_CALLED_SUBS_CI FFFF SMMT_SMS_CENTRE SMSC SMMT_INCOMING_TIMEwhen SG receives a SMS from sc. SMMT_DELIVERY_TIME when sent anacknowledgement to sc. SMMT_CAUSE_FOR_TERMINATION 00000000SMMT_BASIC_SERVICE_TYPE 00 (tele serv.) SMMT_BASIC_SERVICE_CODE 21(SMS-MT) SMMT_CALL_TYPE 00 (incoming) SMMT_MSC_TYPE 02 (GMSC/SG)SMMT_CALLING_NUMBER CLI from sm-data SMMT_CALLING_NUMBER_TON CLI tonSMMT_CALLING_VMSC_NUMBER VMSC-H SMMT_CALLING_NUMBER_NPI 05 (isdn)SMMT_CALLED_NUMBER_NPI 05 (isdn) SMMT_CALLING_VMSC_NUMBERCALLING_SUB_VMSC SMMT_SMS_TYPE 02 (MT) SMMT_CALLED_VMSC_NUMBER VMSC-F

Turning to the case where the initially targeted SG fails after SMSC-Xis told of it by HLR-H, FIG. 51 is a signal flow diagram for a mobileterminated SMS message to an MSISDN-H when the subscriber is in an FPMNand the targeted Signal Gateway (SG) fails, under an embodiment. WhenSMSC-X's MAP MT-SMS to SG1 reaches GMSC-H, since SG1 failed, SG2 SPC2 isthe backup to SG1. GMSC-H forwards the MT-SMS to SPC2 of SG2. SG2 willrelay MT-SMS to VMSC-F whose response is sent back SG2. SG2 then relaysthe response back to SMSC-X except that the calling GT is that of SG1since SMSC-X has SG1 as the called GT when MT-SMS is initiated.

Note that this case is supported by partial fail-over since the MAPtransaction between HLR-H and SMSC-X involves no on-going transactionwith the Signal Gateway function. FIG. 52 is another signal flow diagramfor a mobile terminated SMS message to an MSISDN-H when the subscriberis in an FPMN and the targeted Signal Gateway (SG) fails, under anembodiment.

2.14.3. SMS to MSISDN-H when Subscriber in VPMN

Normal GSM operations apply regardless of whether the SMS is sent bySMSC-H, SMSC-F or SMSC-V. VMSC-V MT SMS CDR is used for SMSInter-working settlements between HPMN and VPMN.

2.14.4. SMS to MSISDN-F when Subscriber in FPMN

Since MSISDN-F is from a specific range of numbers, GMSC-F is configuredwith GTT to route the CdPA=MSISDN-F SCCP message (e.g. SRI/SRI-SM)towards GMSC-H which then routes the message to the Signal Gatewayfunction. Note that GMSC-F can either route SCCP messages on MSISDN-Ftowards HPMN side via an ISC provider which is configured to route theCdPA=MSISDN-F towards the HPMN side or it is configured in its own GTT(of STP-F/GMSC-F) to translate CdPA=MSISDN-F toCdPA=Common-HPMN-GT-of-Signal-Gateway.

The Signal Gateway could immediately return itself as the VMSC-F orSGSN-F. However to avoid recovery situation where HLR might have changedthe VLR or SGSN address without the Signal Gateway knowing about it andthere may be other indicators (e.g. message waiting indicators fromMAP-Inform-Service-Center), so relaying the SRI-SM back to HLR-H onMSISDN-H by replacing MSISDN-F will be important.

Note here that regardless of whether the Signal Gateway function passesVMSC/SGSN transparently or not when location update is sent from FPMN,the Signal Gateway function always return itself as the VMSC/SGSNaddress when the SRI-SM is issued on MSISDN-F rather than the realVMSC/SGSN address. This supports special billing by the Signal Gatewayfunction on MSISDN-F numbers.

FIG. 53 is a signal flow diagram for a mobile terminated SMS message toan MSISDN-F when the subscriber is in an FPMN, under an embodiment. TheSignal Gateway first maps the incoming SRI-SM message from SMSC-X to anew transaction of SRI-SM with HLR-H by replacing the MSISDN-F number byMSISDN-H. The transformation is shown in Table 34.

TABLE 34 SRI-SM from Signal Gateway SRI-SM from SMSC-X to HLR-H viaGMSC-H SCCP Called Address: SCCP Called Address: GT: MSISDN-F GT: HLR-HSSN: 6 SSN: 6 TT: 0 TT: 0 SCCP Calling Address: SCCP Calling Address:GT: SMSC-X GT: SG SSN: 8 SSN: 8 TT: 0 TT: 0 MAP level parameters: MAPlevel parameters: MSISDN: MSISDN-F MSISDN: MSISDN-H

The Ack is transformed as shown in Table 35.

TABLE 35 Ack from Signal Gateway SRI-SM Ack from HLR-H to the SG toSMSC-X via GMSC-H SCCP Called Address: SCCP Called Address: GT: SG GT:SMSC-X SSN: 8 SSN: 8 TT: 0 TT: 0 SCCP Calling Address: SCCP CallingAddress: GT: HLR-H GT: SG SSN: 6 SSN: 6 TT: 0 TT: 0 MAP levelparameters: MAP level parameters: VMSC: SG/VMSC-F IMSI: IMSI-H IMSI:IMSI-H VMSC: SG

The return VMSC field can be SG itself or any VMSC-F from HLR-H. TheSMSC-X issues a FSM message to the Signal Gateway. The message istransformed as shown in Table 36.

TABLE 36 Message from Signal Gateway MT FSM from SMSC-X to VMSC-F viaGMSC-H SCCP Called Address: SCCP Called Address: GT: SG GT: VMSC-F SSN:8 SSN: 8 TT: 0 TT: 0 SCCP Calling Address: SCCP Calling Address: GT:SMSC-X GT: SG SSN: 8 SSN: 8 TT: 0 TT: 0

No MAP level parameters are changed. Note that the Signal Gateway has aHPMN Global Title so there is no concern whether SM-RP-OA is national orinternational since the sending SMSC takes care of this case by makingthe address indicator international as if the subscriber is roaming,irrespective of what subscriber number the sender is sending to.

Since the Signal Gateway also modifies the SCCP Calling Party Address,the confirmation message is also routed back the same way as shown inTable 37.

TABLE 37 Message from Signal Gateway MT FSM Response from VMSC-F toSMSC-X via GMSC-H SCCP Called Address: SCCP Called Address: GT: SG GT:SMSC-X SSN: 8 SSN: 8 TT: 0 TT: 0 SCCP Calling Address: SCCP CallingAddress: GT: VMSC-F GT: SG SSN: 8 SSN: 8 TT: 0 TT: 0

FIG. 54 is another signal flow diagram for a mobile terminated SMSmessage to an MSISDN-F when the subscriber is in an FPMN, under anembodiment.

The Signal Gateway generates a CDR if the message was deliveredsuccessfully. This CDR, to which the example algorithm that followsrelates, may be used to apply a special discount for SIMM subscribers.

SMMT CDR SMMT_CALL_REFERENCE SMMT_EXCHANGE_ID SG SMMT_CALLED_IMSI SIMMsubscriber IMSI SMMT_CALLED_IMEI FFFF . . . SMMT_CALLED_NUMBER NDC|B(MSISDN-F) SMMT_CALLED_NUMBER_TON 05 (international)SMMT_CALLED_SUBS_LAC FFFF SMMT_CALLED_SUBS_CI FFFF SMMT_SMS_CENTRE SMSCSMMT_INCOMING_TIME when SG receives a SMS from sc. SMMT_DELIVERY_TIMEwhen sent an acknowledgement to sc. SMMT_CAUSE_FOR_TERMINATION 00000000SMMT_BASIC_SERVICE_TYPE 00 (tele serv.) SMMT_BASIC_SERVICE_CODE 21(SMS-MT) SMMT_CALL_TYPE 00 (incoming) SMMT_MSC_TYPE 02 (GMSC/SG)SMMT_CALLING_NUMBER CLI from sm-data SMMT_CALLING_NUMBER_TON CLI tonSMMT_CALLING_VMSC_NUMBER VMSC-X SMMT_CALLING_NUMBER_NPI 05 (isdn)SMMT_CALLED_NUMBER_NPI 05 (isdn) SMMT_CALLING_VMSC_NUMBERCALLING_SUB_VMSC SMMT_SMS_TYPE 02 (MT) SMMT_CALLED_VMSC_NUMBER VMSC-F2.14.5. SMS to MSISDN-F when Subscriber in XPMN

Collectively, for the purposes of this scenario, HPMN and VPMN arereferred to here as XPMN. Since MSISDN-F is from a specific range ofnumbers, GMSC-F is configured with GTT to route the SRI-SM requesttowards GMSC-H which then routes the SRI-SM to the Signal Gateway withSCCP Called Party Address as MSISDN-F. The Signal Gateway transforms themessage as shown in Table 38.

TABLE 38 Message from Signal Gateway SRI-SM from SMSC-X to HLR-H viaGMSC-H SCCP Called Address: SCCP Called Address: GT: MSISDN-F GT:MSISDN-H SSN: 6 SSN: 6 TT: 0 TT: 0 SCCP Calling Address: SCCP CallingAddress: GT: SMSC-X GT: SG SSN: 8 SSN: 8 TT: 0 TT: 0 MAP levelparameters: MAP level parameters: MSISDN: MSISDN-F MSISDN: MSISDN-H

The SRI-SM response is routed back to the Signal Gateway since the SCCPCalling Party Address was modified too. The response is translated asshown in Table 39.

TABLE 39 Message from Signal Gateway SRI-SM Response from HLR to SMSC-Xvia GMSC-H SCCP Called Address: SCCP Called Address: GT: SG GT: SMSC-XSSN: 8 SSN: 8 TT: 0 TT: 0 SCCP Calling Address: SCCP Calling Address:GT: HLR-H GT: SG SSN: 6 SSN: 6 TT: 0 TT: 0 MAP level parameters: MAPlevel parameters: IMSI: IMSI-H IMSI: IMSI-H MSC: VMSC-X MSC: SG

The SMSC-X issues a FSM message to the Signal Gateway. The message istransformed as shown in Table 40.

TABLE 40 Message from Signal Gateway MT FSM from SMSC-X to VMSC-X viaGMSC-H SCCP Called Address: SCCP Called Address: GT: SG GT: VMSC-X SSN:8 SSN: 8 TT: 0 TT: 0 SCCP Calling Address: SCCP Calling Address: GT:SMSC-X GT: SG SSN: 8 SSN: 8 TT: 0 TT: 0

No MAP level parameters are changed. Since the Signal Gateway alsomodifies the SCCP Calling Party Address, the confirmation message isalso routed back the same way as shown in Table 41.

TABLE 41 Message from Signal Gateway MT FSM Response from VMSC-X toSMSC-X via GMSC-H SCCP Called Address: SCCP Called Address: GT: SG GT:SMSC-X SSN: 8 SSN: 8 TT: 0 TT: 0 SCCP Calling Address: SCCP CallingAddress: GT: VMSC-X GT: SG SSN: 8 SSN: 8 TT: 0 TT: 0

FIG. 55 is a signal flow diagram for a mobile terminated SMS message toan MSISDN-F when the subscriber is in an VPMN, under an embodiment.

The Signal Gateway generates a CDR if the message was deliveredsuccessfully. This CDR, to which the example algorithm that followsrelates, may be used to apply a special discount for SIMM subscribers.

SMMT CDR SMMT_CALL_REFERENCE SMMT_EXCHANGE_ID SG SMMT_CALLED_IMSI SIMMsubscriber IMSI SMMT_CALLED_IMEI FFFF . . . SMMT_CALLED_NUMBER NDC|B(MSISDN-F) SMMT_CALLED_NUMBER_TON 05 (international)SMMT_CALLED_SUBS_LAC FFFF SMMT_CALLED_SUBS_CI FFFF SMMT_SMS_CENTRE SMSCSMMT_INCOMING_TIME when SG receives a SMS from sc. SMMT_DELIVERY_TIMEwhen sent an acknowledgement to sc. SMMT_CAUSE_FOR_TERMINATION 00000000SMMT_BASIC_SERVICE_TYPE 00 (tele serv.) SMMT_BASIC_SERVICE_CODE 21(SMS-MT) SMMT_CALL_TYPE 00 (incoming) SMMT_MSC_TYPE 02 (GMSC/SG)SMMT_CALLING_NUMBER CLI from sm-data SMMT_CALLING_NUMBER_TON CLI tonSMMT_CALLING_VMSC_NUMBER VMSC-X1 SMMT_CALLING_NUMBER_NPI 05 (isdn)SMMT_CALLED_NUMBER_NPI 05 (isdn) SMMT_CALLING_VMSC_NUMBERCALLING_SUB_VMSC SMMT_SMS_TYPE 02 (MT) SMMT_CALLED_VMSC_NUMBER VMSC-X22.15. Mobile Originated SMS

For all practical purposes, it is assumed that the SIMM subscriber usesone of the HPMN SMSC for sending mobile originated SMS messages. HoweverSMSC-S-H is a special HPMN SMSC address to be used as a SMSC address inthe SIM of SIMM subscribers. In the Insert Subscriber Data messagerouted from HPMN to a FPMN where MSISDN-H was changed to MSISDN-F, allSMS messages originating from such a FPMN will have MSISDN-F as thesender address.

Unlike MO-calls, MO-SMS is always going thru the Signal Gateway. As aresult, the Signal Gateway is capable of changing the caller ID based onthe destination number of the message irrespective of the network (FPMNor HPMN or VPMN) the subscriber registered on. If the destination numberis from a FPMN country, then the caller ID can be changed to thesubscriber's FPMN number unless it is set not to be automaticallychanged by the Signal Gateway via the USSD command **123*2#. Conversely,if the destination is HPMN or VPMN, then the caller ID can be changed toMSISDN-H.

For example, when the SIMM subscriber registered with FPMN sends a SMSto a non-FPMN country number, the sender's address should be changed toMSISDN-H unless the subscriber sets the option otherwise. When FPMN isregistered, SMSC-S-H is used instead of SMSC-H for a normal subscriber.The SMSC-S-H is a GT that HPMN GMSC-H/GTT translates to a SignalGateway. When a FPMN registered SIMM subscriber sends a MO-SMS toSMSC-S-H. The MO-SMS reaches the Signal Gateway. The Signal Gateway thenrelays it to the real SMSC-H after converting MSISDN-F to MSISDN-H andothers.

FIG. 56 is a signal flow diagram for a mobile originated SMS message,under an embodiment.

2.16. SMS Re-Delivery Management

In the case of an SMS sent to the MSISDN-H number by a SMSC-X, becausethe Signal Gateway always forward SMS delivery status back to theSMSC-X, SMSC-X will only need to inform HLR-H for delivery report (e.g.,to set message waiting data). Subsequent interactions regarding AlertService Center and Inform Service Center are between the HLR-H and theSMSC-X directly. The Signal Gateway function will not be involved.

Ready-For-SMS map message on IMSHI-H for a SIMM subscriber is handledtransparently by the Signal Gateway function.

However because the Signal Gateway functions like a virtual HLR to theMSISDN-F number of a SIMM subscriber, when SRI-SM was sent onCdPA=MSISDN-F, the Signal Gateway function is the responding entity orHLR to the SMSC-X. This means that delivery report status due to failurewill be sent by the SMSC-X to the Signal Gateway. Subsequentinteractions regarding Alert-Service-Center and Inform-Service-Centerwill also be between the SMSC-X and the Signal Gateway.

The Signal Gateway first maps the incoming ReportSM Delivery messagefrom SMSC-X to a new transaction of ReportSM with HLR-H by replacing theMSISDN-F number by MSISDN-H. The transformation is as shown in Table 42.

TABLE 42 ReportSM from Signal Gateway ReportSM from SMSC-X to HLR-H viaGMSC-H SCCP Called Address: SCCP Called Address: GT: MSISDN-F GT: HLR-HSSN: 6 SSN: 6 TT: 0 TT: 0 SCCP Calling Address: SCCP Calling Address:GT: SMSC-X GT: SG SSN: 8 SSN: 8 TT: 0 TT: 0 MAP level parameters: MAPlevel parameters: MSISDN: MSISDN-F MSISDN: MSISDN-H

The Ack is transformed as shown in Table 43.

TABLE 43 Ack from Signal Gateway ReportSM Ack from HLR-H to the SG toSMSC-X via GMSC-H SCCP Called Address: SCCP Called Address: GT: SG GT:SMSC-X SSN: 8 SSN: 8 TT: 0 TT: 0 SCCP Calling Address: SCCP CallingAddress: GT: HLR-H GT: SG SSN: 6 SSN: 6 TT: 0 TT: 0 MAP levelparameters: MAP level parameters: MSISDN-alert: MSISDN-H MSISDN-alert:MSISDN-H

FIG. 57 is a signal flow diagram for SMS message re-delivery management,under an embodiment.

To the HLR-H in this case, the Signal Gateway that sent theReportSM-Delivery will be the SMSC-X to send Alert-Service-Center whenready-for-SM is received. Similar actions for Inform-Service-Center willalso be performed when SRI-SM is issued from the Signal Gateway to theHLR-H, as shown in Table 44.

TABLE 44 AlertSC from the Signal Gateway AlertSC from HLR-H to SMSC-Xvia GMSC-H SCCP Called Address: SCCP Called Address: GT: SG GT: SMSC-XSSN: 8 SSN: 8 TT: 0 TT: 0 SCCP Calling Address: SCCP Calling Address:GT: HLR-H GT: SG SSN: 6 SSN: 6 TT: 0 TT: 0 MAP level parameters: MAPlevel parameters: MSISDNAlert: MSISDN-H MSISDNAlert: MSISDN-F

FIG. 58 is another signal flow diagram for SMS message re-deliverymanagement, under an embodiment.

3. SIMM Roaming Variations

The SIMM service for roaming is a subscription-based service thatprovides a local number at each partner network for a subscriber, but isnot so limited. The local number can be assigned to a subscriberpermanently or temporarily depending upon operator requirements. TheSIMM service for roaming is generally applied by an HPMN operator for(international and national) outbound roamers at partner Foreign PMN(FPMN) networks involving some logistical arrangements at FPMNs. Howeverthe SIMM solution for roaming can also be applied to (national orinternational) inbound roamers without involving any HPMN logistics. Inparticular, it can be deployed for a Mobile Virtual Network Operator(MVNO).

So far, the document has primarily focused on

SIMM roaming for international roaming and for outbound roamers forpermanent local numbers has been described above. Before continuing, inthis section, adaptations of the SIMM roaming solution are describedthat provide temporary local numbers, national roaming and inboundroaming, and MVNO.

3.1. Temporary MSISDN-F

Instead of assigning a permanent MSISDN-F of a FPMN when the SIMMsubscriber is roaming on the FPMN network, the Signal Gateway can assigna temporary MSISDN-F based on operator requirements. The operator caneven choose to provide a permanent MSISDN-F for some subscribers (e.g.,high end customers such as frequent business travelers) and a temporaryMSISDN-F for other subscribers (e.g., low end customers such asoccasional visitors who would otherwise buy a local prepaid). Theoperator can in particular offer cheaper subscription fees or evenduration-based rental fees for subscribers who just want a temporaryMSISDN-F.

From a signaling and logistics perspective, temporary or permanentMSISDN-F makes no difference. However to accommodate the temporaryMSISDN-F, the Signal Gateway maintains a pool of MSISDN-F intended fortemporary use. When a SIMM subscriber is roaming at an FPMN, the SignalGateway first checks if the subscriber has already an assigned MSISDN-F(permanent or temporary), if not the Signal Gateway will select aMSISDN-F from the pool to assign to the SIMM subscriber at FPMN.

To track the temporary MSISDN-F assignment to facilitate the recycle ofassigned temporary MSISDN-F back to the pool of free MSISDN-F, theSignal Gateway of an embodiment also maintains a database of records onassigned temporary MSISDN-F that contains MSISDN-H of the assignment,the time of the assignment and the last time of its reference (e.g.registration, call or SMS).

Depending on operator requirements, the duration of temporary MSISDN-Fcan be a fixed duration (e.g., 1 week) for each entire use or a fixedduration (e.g., 3 days) after the last time of its reference. Since theSIMM roamer often gives out his/her temporary MSISDN-F at FPMNcountry/region, it is also possible for the roamer to extend theduration via a SMS or USSD command just in case a caller from FPMNcountry/region calls that number a while after he left thecountry/region. The operator can charge the extension on a per dayextension basis.

3.2. National Outbound Roaming

Although the description herein provides details on internationaloutbound roaming, the SIMM solution is equally applicable to nationalroaming. This is usually applied to large countries such as India andChina where national roaming costs are significant compared to thetariffs of local calls. For example, China Mobile consists of manyprovisional operators. A GuangDong Mobile (GMCC) SIMM subscriber whogoes to Beijing can obtain a Beijing Mobile (BMCC) local number.

Although China Mobile, for example, provides optimal routing alreadywithin their own network and the tariff of mobile originated call whenroaming is close to that of a mobile originated call made at home, alocal number at a region/province for a nationally outbound roamer isstill useful for receiving calls outside the China Mobile network whichis not optimally routed. For example, when the GMCC roamer goes toBeijing and obtains a BMCC local number, if the Beijing caller is from afixed line phone or a China Unicorn customer, then the call will berouted to GuangDong first and then re-routed back to Beijing, costingcaller a long distance call and the roamer a long distance reroutedcall. In India, there is also significant tariff difference betweenMO-call when roaming and MO-call made at home.

From a signaling and logistics perspective, international outboundroaming and national outbound roaming are equivalents. However sincenational roaming is within the same country, there will not be anysignaling protocol conversions or ISC involved. This will also simplifythe logistics of treating the Signal Gateway as the virtual HLR of thoseFPMN MSISDN-Fs as MAP signaling on MSISDN-F (SRI, SRI-SM, etc.) can justfollow a normal SCCP GTT on DPC rather than on a special leased line oron global title modification in order to cross international boundaryvia an ISC operator.

3.3. Inbound Roaming

SIMM roaming for inbound roaming is another variation that does notinvolve HPMN logistics. Examples are provided in national roaming and ininternational roaming to illustrate the application of SIMM roaming.

3.3.1. National Inbound Roaming

As an example, an inbound roamer of GMCC registers with China Unicom atBeijing. Generally, a GMCC subscriber cannot register with China Unicom;however in this case, China Unicom accepts the GMCC registration andsends messages on CdPA=MGT-of-GMCC thru the Signal Gateway. The SignalGateway determines if the GMCC IMSI is a subscriber of the temporarylocal number service. If it is not, registration will be rejected. If itis, the registration message will be relayed to the GMCC except that thecalling GT aid VLR and VMSC will be modified to a Signal Gateway GT.Conversely, the HLR from GMCC will also be modified to a Signal GatewayGT and a temporary local number of China Unicom will be replacing theGMCC MSISDN-H of the subscriber.

The Signal Gateway will be located in an SS7-based network so that theGMCC network sees the subscriber as roaming into an acceptable operator,e.g., a MVNO operator that has its own MCC/MNC or CC/NDC. There are fewif any differences in normal SIMM signaling.

Again the temporary local number can be permanent based on operator(e.g. the MVNO operator) and SIMM subscriber requirements. Thesubscriber can change its caller ID at any time via USSD. The MVNOoperator can also choose to change caller ID automatically via an INinterface at China Unicom if this is supported as indicated in the INgeneral interface section mentioned before.

The MVNO can sell the temporary/permanent local number services directlyto the GMCC subscribers (more accurately to the enterprises employees)without requesting them to change their SIMs and GMCC subscription. TheMVNO can charge the subscribers on a monthly fee or a rental fee per day(e.g. 1 chinese dollar per day) for free incoming calls. China Unicomdoes not charge the GMCC subscribers of the service. Instead, it chargesthe MVNO operator. The MVNO operator can arrange to have bulk or wholesale relationship with China Unicom while it makes it margin thru theretailing relationship with enterprise customers.

3.3.2. International Inbound Roaming

As an example, an international inbound roamer comes to Macau. Whenfirst registered with Smartone Macau, he will receive a welcome SMSindicating that he could get a temporary local number for a fee of fivedollar per day for free incoming calls from Macau provided he isregistered at Smartone Macau at the time of the incoming calls. He cancall Smartone Macau customer care number to turn this on or use the##Send service of an embodiment to activate the assignment of atemporary local number which will be sent to his phone as a SMS message.

Once the temporary local number is activated, the Signal Gateway willissue an InsertSubscriberData to the Smartone Macau VLR location of thesubscriber. To make it possible, an inbound roamers registration isdirected thru the Signal Gateway in the first place. The signaling andcall flows will be similar to SIMM roaming for international outboundroaming except that the Signal Gateway in this case is located at aVPMN.

When the registration message UpdateLoc is routed thru the SignalGateway, the Signal Gateway relays the message by modifying the callingGT but not the VLR to a Signal Gateway GT corresponding to the VLR whilethe VMSC address and the called party address remain the same. Onreceiving InsertSubData from HLR, the Signal Gateway again modifies thecalling GT to be the Signal Gateway GT that correspond to the HLR. TheSignal Gateway however does not modify the real HLR in UpdateLoc Ack sothe VLR has the real HLR. Signal gateway also remembers the real HLR,VLR, VMSC involved in the transaction. The roamers can also changecaller ID via USSD like standard SIMM solution except that in this case,USSD has to be VPMN service code since the Signal Gateway is located atVPMN. If USSD is not possible, the ##SEND service of an embodiment canbe deployed.

To avoid all signaling on CdPA=MGT going thru the Signal Gateway forinbound roamers, the MGT range can be limited to certain networks orcertain countries. The SIMM Signal Gateway can also be integrated withthe SRS platform of an embodiment which is used to extend virtualroaming relationships for an operator such as Smartone Macau. In thisexample, all signaling relating to inbound roamers from operators thatdo not have direct roaming relationships with Smartone Macau are routedthru the SRS gateway which then represents the VPMN network as that ofSmartone HK which has the roaming relationships.

Smartone Macau currently has deployed the SRS using Smartone HK as thesponsoring operator for roaming relationships. Smartone Macau canfurther extend the service to encourage the inbound roamers (fromoperators that do not have a direct roaming relationships with SmartoneMacau) to register with its network by offering a temporary local numberservice for these inbound roamers. In this way, when they make localcalls (including those to HK), their caller ID will be the temporaryMacau numbers. When they receive calls on the temporary Macau numbersfrom any operator (including fixed line) or from HK, it will be a cheapcall rather than an internationally re-routed call. Note that thetemporary local number call is slightly different from optimal routingoffered by an embodiment. The temporary local number call applies acrossoperators and countries. For example, the HK call to a Macau number ischeaper for the inbound roamer from England and the caller from HK.

Finally, if caller ID is not important for the inbound roamer whorequests a temporary local number, there is a more simplified solution.In this solution, normal registration of the roamer will apply with noinvolvement of a Signal Gateway. However roamers registrationtransactions are monitored on the roaming links. A temporary number isassigned on demand and maintained within the roamer DB of thesubscriber. When the roamer makes a call or sends an SMS, there is nodifference in signal flow. However when the roamer receives a call onthe temporary number, the Signal Gateway is viewed as the HLR of thesetemporary numbers. The Signal Gateway then issues a PRN request to thereal VLR of the subscriber from the roamer DB. When the roamer receivesSRI-SM query on the temporary number, the query is sent to the SignalGateway which returns the real VMSC from the roamer DB of thesubscriber.

3.4. SIMM for MVNO

In the national roaming for inbound roaming example, the use of a MVNOthat has its own MCC/MNC or CC/NDC has been described. The MVNO can alsobe used in international roaming.

For example, today a Taiwanese operator (e.g., TCC) is not allowed tosell its MSISDNs to China Mobile for the China Mobile outbound roamersregistering on the operator due to regulatory restrictions in Taiwan. Toavoid this problem, a MVNO can be introduced. The Taiwanese operatorsimply sells its MSISDN-F to the MVNO operator. When the SIMM subscriberfrom China Mobile is registering with TCC, TCC can route message onCdPA=MGT-ChinaMobile-special-range thru the Signal Gateway located inthe MVNO.

The MVNO can relay the message to China Mobile by modifying the callingGT and VLR/VMSC to be a Signal Gateway GT (from the MVNO operator)without changing the Called GT. The Signal Gateway will modify MSISDN-H(China Mobile) into MSISDN-F (TCC MSISDN) accordingly. The number couldbe permanent or temporary. Normal SIMM signaling and call flows apply.

4. SIMM Roaming Variation Using any FPMN Number

The SIMM Service/System describer herein uses an FPMN number that is ina special range defined by the FPMN. The reason for the FPMN number in aparticular range is because there is no profile or IMSI associated withthese numbers at the FPMN. The SIMM Signal Gateway is the HLR for thesespecially ranged FPMN numbers. All call-related and non-call relatedsignaling messages on these FPMN numbers go through the Signal Gateway.As a result, no HLR entry in the FPMN is required and a single profileis defined by HPMN for any number of FPMNs. However, this means that theSIMM Service can not use existing FPMN numbers or just any FPMN number.

A variation of SIMM roaming described below, however, supports SIMMService using any FPMN number including any existing FPMN numbersassigned to the subscriber. This variation uses an FPMN profile for thesubscriber at the FPMN in addition to the subscriber's HPMN profile.Consequently, this variation allows for the use of any FPMN numberwithout the need for special signaling on the FPMN number to the HPMNnetwork. Alternative embodiments may use a hybrid in which one FPMNmakes use of any FPMN number approach under the variation while anotherFPMN uses FPMN numbers in the specified range, as described herein.

The variation of SIMM roaming that supports SIMM Service using any FPMNnumber is implemented under partnership and non-partnership embodimentsas described below. Under the partnership embodiment, for example, eachFPMN provides a maximum profile or at least the profile of the HPMN. Thesubscriber does not have a FPMN SIM and hence does not know the IMSI andKi associated with the IMSI. Special billing relationships are in placefor the subscriber at FPMN networks. Special routing arrangements overleased line are also in place for rerouted calls to cut down reroutingcost for the subscribers. The subscriber receives a single bill from theHPMN only for the services.

Turning to the non-partnership embodiment, generally, the subscriberalready has an FPMN number but the subscriber may get a new FPMN number.There will be a bill from the HPMN, and each FPMN operator with whichthe subscriber has an FPMN number. There are no special billingrelationship and no prearranged leased lines to cut down rerouting cost.When the subscriber is in an FPMN network, despite having a localnumber, the FPMN still treats him/her as a roamer and chargesaccordingly. The HPMN either passes this cost to the subscriber orabsorbs the cost (of the difference between roaming and local) so thesubscriber still feels like he/she is at home when in the FPMN network.Since the subscriber also has an FPMN SIM, he/she can put the SIM in thehandset when in the FPMN where billing is done locally. However in thiscase, the subscriber will not be able to receive calls and SMS messagesfrom the HPMN and his/her other FPMN numbers. Under both the partnershipand non-partnership embodiments where the HPMN SIM is used, thesubscriber will be able to receive calls, SMS on any HPMN or FPMNnumber.

The SIMM roaming variation for any FPMN number of an embodiment supportsuse of different profiles in the HPMN/FPMN. For example, one profile isGPRS allowed, incoming calls when roaming allowed, while another profileis GPRS allowed, incoming calls when roaming not allowed. Anotherexample includes the case where one profile is Camel and the other issomething other than Camel. Under the partnership embodiment, thedifferent profiles can be synchronized logistically, while thenon-partnership embodiment requires the subscriber to ensure profilesare synchronized in order to provide seamless service in the differentpartner networks. For example, under the first example above, withoutsynchronization the subscriber having an FPMN profile that does notallow incoming calls when roaming will not be able to receive calls whenin the HPMN.

When operating under the variation of SIMM roaming that supports SIMMService using any FPMN number and registering at a network (for exampleXPMN) with HPMN SIM, since the HPMN IMSI is in a special range, thesignaling is via the Signal Gateway. The signal gateway relays thesignal to the real HPMN HLR. At each successful registration, the signalgateway also issues a registration to each FPMN with which thesubscriber has an FPMN number. The signal gateway appears as a VLR orSGSN to these FPMN HLRs. Unlike the special range approach, even forlocal signaling, it will be fully relayed thru the Signal Gateway inboth directions, not just one direction. While the HPMN profile is sentto the VLR, the FPMN profile is not. For example, if the FPMN profiledoes not allow outbound calls when roaming or roaming restricted orroaming not allowed, it will not affect the VLR profile at HPMN. So MMS,GPRS, and Camel will adhere to the HPMN IMSI profile.

Regarding MO-calls/MO-SMS, when the subscriber is in the HPMN,MO-calls/MO-SMS are billed as normal HPMN subscribers. When thesubscriber is in the FPMN, depending on the operator-subscriberarrangement and whether operations are under the partnership ornon-partnership embodiment, roaming charges or local airtime charges mayor may not apply. Also depending on destination number, caller ID can bemodified to one of the subscriber's numbers.

Regarding MT-calls, when the subscriber is in the HPMN/VPMN, calls onthe MSISDN-H follow the normal signal flow. Calls on the MSISDN-Finvolve the HLR-F issuing PRN to the Signal Gateway and the SignalGateway retrieves the MSRN from the real VLR and returns the MSRN or avariation back to the HLR-F. One possible alternative is that, under thepartnership embodiment, special rerouting and billing can be controlled.Also if the VPMN is in the same country as FPMN, then optimal routingmight be allowed.

Further, when the subscriber is in the FPMN, MT-calls on MSISDN-H arererouted from HPMN to FPMN. The PRN from HLR-F comes to the signalgateway which in turn sends it to VLR-F. Again the MSRN returned canvary depending on the partnership embodiment where special rerouting orbilling can be applied. Calls on MSISDN-F are then optimally routed. ThePRN query from HLR-F comes to the Signal Gateway which in turn sends itto VLR-F. The MSRN returned is sent directly back to HLR-F.

Regarding MT-SMS, when the subscriber is in the HPMN, SMS on MSISDN-Hare in accordance with the normal signal flow. SMS on MSISDN-F isrelayed thru the Signal Gateway where at least one of spam filtering canbe applied, SMS interworking can be charged, and SMS delivery can bemanaged from an HPMN perspective.

When in the FPMN, MT-SMS on MSISDN-H will be again relayed thru theSignal Gateway to the VMSC-F. SMS on MSISDN-F will be also be relayedthru the Signal Gateway first before being sent to the VMSC-F.

5. Miscellaneous Interfaces

5.1. Number Portability Considerations

The number portability domain considered is within a country.Subscribers who port a SIMM service number to another operator will nolonger have access to this service. Their IMSI and all MSISDN-H toMSISDN-F mappings are deleted from the Signal Gateway. Other operationslike removing the subscriber from the HLR and adding entries to NumberPortability database are performed independent of the Signal Gateway.Since the ported-out MSISDN will now be associated with the IMSI ofanother operator, the MGT-based routing is not received at HPMN.However, the HPMN GMSC still performs Number Portability lookup androuting of calls to the PMN currently serving the ported-out MSISDN.

Subscribers are allowed to port-in their existing numbers from otheroperators in the country of the HPMN. This is the case where frequentroamers from other networks decide to churn in order to have thisservice available. Normal operations like adding a new subscriber (byassigning a SIM with IMSI in the SIMM range) in the HLR and associatingthe ported-in number, and adding the ported-in number to the NumberPortability database, etc., are outside the scope of the Signal Gateway.Through the Signal Gateway provisioning interface, this IMSI is mappedto MSISDN-H and MSISDN-F at the Signal Gateway subscriber DB.

For signaling messages (Update Location, for example) routed on MGT forthis subscriber, since the IMSI belongs to HPMN, the messages will getrouted to HPMN. The ported-in MSISDN-H will be returned in the InsertSubscriber Data message and substituted with MSISDN-F when thesubscriber is roaming in an FPMN. The HPMN GMSC handles signalingmessages routed on the MSISDN-H (when not routed via the SignalGateway). For signaling messages routed on the MSISDN-F, there areseveral options available including, but not limited to: the SignalGateway routes the messages directly to the HLR by mapping the MSISDN-Fto MSISDN-H and looking up corresponding IMSI range mapping to HLR(recommended); the Signal Gateway maps MSISDN-F to MSISDN-H and routesthe message via the HPMN GMSC/STP (the GMSC/STP is responsible forlooking up the Number Portability database and forwarding the signalingmessage) (also recommended); and the Signal Gateway maps MSISDN-F toMSISDN-H, interfaces to the Number Portability database, retrieves therouting number and sends it to GMSC/STP for further routing (hisapproach uses an interface to the Number Portability Database, but isnot so limited).

If the MSISDN-F is ported out, FPMN GMSC is responsible for handling thesignaling in the typical way for a ported out number (e.g., does notroute messages on CdPA=ported-out-MSISDN-F towards GMSC-H and the SignalGateway function) and hence these messages will never reach the SignalGateway. If a number in FPMN is ported-in and needs to be part of theSIMM service, then the FPMN GMSC configures to route the signalingmessages for this MSISDN to the Signal Gateway. This is similar to thecase where FPMN ports one number from a HLR to another HLR. The SignalGateway is the port-in HLR in this case. The Signal Gateway simply addsthe ported in number to its subscriber DB.

5.2. Location-Based Services

Location-based services include SMLC and GMLC. The SMLC is like a VLR inthat it determines the positioning method and determines the position ofa MS based on MS's measurements of LMUs. These location measurementunits are to the SMLC like a VMSC is to the VLR. The GMLC provides alocation interface for LCS (location service) clients to requestlocation information about a targeted MS.

SRI-LCS is a MAP message between GMLC and HLR that operates on IMSI andMSISDN to locate the VMSC to request location information of a MS. Ifthe message is on MSISDN-H, it has nothing do with the Signal Gatewayfunction except returning SG as VMSC if the SIMM subscriber isregistered on FPMN. However if the message is on MSISDN-F, then theSignal Gateway maps the message by replacing MSISDN-F by MSISDN-H whenrelaying the message to HLR-H. It also returns the Signal Gateway itselfto the GMLC.

Provide Subscriber Location (PSL) is a MAP message between GMLC and VMSCto request location information of a target MS that operates on IMSI andMSISDN. When the SIMM subscriber is registered in FPMN, the VMSC to GMLCis the Signal Gateway itself. Thus in this case, if the message is onMSISDN-H, the Signal gateway will map the message by replacing MSISDN-Hby MSISDN-F and impersonating the GMLC to the real VMSC; if the messageis on MSISDN-F, the Signal Gateway will simply relay the message to thereal VMSC.

The SRI-LCS and PSL are analogous to SRI and PRN for call services.However there is no analogy for SLR service which arises when a requestfor location is either implicitly administered or made at some earliertime by PSL. For Subscriber Location Report service between VMSC andGMLC which also operates on MSISDN and IMSI, special handling is usedwhen the subscriber registers at FPMN. In this case, when message issent to the Signal Gateway by VMSC-F on MSISDN-F, the Signal Gatewayreplaces the MSISDN-F by MSISDN-H before relaying on to the originalrequesting GMLC if the original requesting GMLC is asking locationinformation on MSISDN-H; the MSISDN-F is not replaced if the originalrequesting GMLC is asking location information on the MSISDN-F.

5.3. Multiple HPMN Support in a Central Location

The Signal Gateway function of an embodiment supports multiple HPMNs inaddition to multiple FPMNs. The platform is hosted or managed in oneHPMN or by a third party service provider although different HPMNs willhave their secure access to provision for their own subscribers and toexamine and process their own CDRs. The platform will access the SS7networks of each HPMN. Where there are signal protocol variants, specialsignaling conversion over leased lines is performed. Further more, GTTconfiguration between the hosting network and the targeting network isperformed to pass messages routed on CdPA=MSISDN-F/MSISDN-H. FIG. 59 isa signal flow diagram for multiple HPMN support, under an embodiment.

Voice trunk calls can occur directly between the FPMN and HPMN, but arenot so limited. The ISUP loopback or IN signaling are performed via acommon platform hosted in one HPMN or by a third party service provider.

A centrally hosted Signal Gateway for several HPMN operators means thatonly one operator or party need be responsible for the management andlogistics of the Signal Gateway. In addition, hardware costs are sharedamong the HPMN operators.

5.4. Signal Gateway Recovery Procedure

When a SIMM subscriber registers at FPMN, the Signal Gateway maintainsthe information on the true VMSC-F and VLR-F in which the roamer iscurrently located. Additional dynamic information that needs to bemaintained is between original FTN and the temporary, substituted FTNsent to the VLR-F in Insert Subscriber Data message. The data ismaintained in memory; and also stored on DB of mirrored disks. It isalso periodically backed-up into a non-volatile storage.

Since the Signal gateway is a virtual VLR and a virtual HLR, allinformation maintained at the Signal Gateway is transitional and can beestablished by interactions with VLR-F and HLR-H. There will be noindicators about the status of real VLR stored in the Signal Gateway.The Signal Gateway will just map whatever incoming messages to the realdestinations. Also, since the HLR information is obtained upon alocation update at FPMN by the Signal Gateway function, VLR restorationprocedure at the Signal Gateway is unnecessary. The MAP-Reset to thereal VLR-F by the faulty Signal Gateway's recovery procedure will besufficient to automatically obtain the HLR data.

FIG. 60 is a signal flow diagram for Signal Gateway (SG) recovery, underan embodiment. Regarding recovery of the Signal Gateway, when the VLRfails, the VLR issues MAP-Restore on an affected IMSI. For MAP-Restoreon a SIMM IMSI, the Signal Gateway simply relays the message to thecorresponding HLR-H. Similarly when HLR fails, MAP-Reset will be issuedto the Signal Gateway when the SIMM subscriber registers at FPMN. TheSignal Gateway thus relays the MAP-Reset message to the real VLR-F.

Now after a recovery/restart operation of the Signal Gateway, allroaming records affected in the system are marked as “Not Updated”. Forall SIMM subscribers, the Signal Gateway issues a SRI-SM using SCCPCalled Party Address as MSISDN-H. The HLR returns the IMSI and MSCaddress. If the MSC address is not in FPMN, the corresponding record inthe Signal Gateway is deleted. If the MSC address is the Signal Gatewayaddress, the corresponding record is marked as “Not Updated”. This isbecause the only concern is for SIMM subscribers in FPMN. However theSRI-SM part could flood the HLR-Hs, it is only treated as an option anddoes not affect the overall recovery procedure.

For each IMSI of a “Not Updated” record, if the VLR address of therecord is not null it is put in the set of Reset-VLR, and if the SGSNaddress of the record is not null it is put in the set of Reset-SGSN.For each VLR in Reset-VLR, the Signal Gateway issues a MAP-Reset to theVLR with SG as the HLR number in the MAP-Reset message. This causes theVLR-F to issue Updatelocation after radio contact is established. Thisalso causes HLR-H to insertSubData to the Signal Gateway function. Foreach SGSN in Reset-SGSN, the Signal Gateway issues a MAP-Reset to theSGSN with SG as the HLR number in the MAP-Reset message. This causes theSGSN-F to issue UpdateGPRSlocation after radio contact is established.This also causes HLR-H to insertSubData to the Signal Gateway function.

Alternatively for each IMSI of a “Not Updated” record, the SignalGateway issues a MAP-Reset to the VLR if the VLR field is not empty andissues a MAP-Reset to the SGSN if the SGSN field is not empty. In bothcases, either HLR number or HLR number list containing the IMSI could beused in the MAP-reset message. This causes the VLR-F/SGSN-F to issueUpdatelocation/UpdateGPRSlocation after radio contact is established.This also causes HLR-H to insertSubData to the Signal Gateway function.

Unlike a real VLR, upon receipt of a MAP_PROVIDE_ROAMING_NUMBERindication from a HLR-H for an IMSI that is unknown in the SG's roamerrecord, the Signal Gateway simply issues error ack back to the HLR-H. Ifthe IMSI is known, since there is no status indicator at the SignalGateway, the Signal Gateway issues PRN to the real VLR-F if known. Afterthat, normal restoration procedure and status indicator management atthe real VLR-F occurs.

The SG restoration procedure results in updating of VMSC-F number, VLR-Fnumber, SGSN number and, if provided by the VLR-F, LMSI in the SG.Consistency of subscriber data that are stored in the VLR-F for an MSthat has been affected by a SG fault with the subscriber data stored inthe SG for this MS is achieved.

As an implementation option, a notification can be forwarded to the MSto alert the subscriber to check the parameters for supplementaryservices that allow subscriber controlled input(MAP_FORWARD_CHECK_SS_INDICATION service). If the VLR-F or SGSN-Freceives this notification from the SG it shall forward the notificationto the MS. The figure below illustrates the signaling sequence for SGrestoration.

After a restart, the Signal Gateway performs the following actions forthe subscriber data records that have been affected by the SG fault, butis not so limited: reload the all roamer data from a non-volatile backup; if the MAP_FORWARD_CHECK_SS_INDICATION service is required, markeach subscriber record “SS Check Required” by setting the “Check SS”indicator; and send a MAP_RESET request to the VLR-Fs or SGSNs where itsMSs are located.

The MAP_RESET request contains the SG number and optionally the HLRIdentity List. When receiving a MAP_RESET indication, the VLR-F derivesall involved MSs of that SG either from the HLR Identity List (ifpresent) or from the SG number. The VLR-F will then mark these MSs withthe indicator “Location Information Confirmed in HLR” set to “NotConfirmed” and will deactivate all subscriber tracings for these MSs.

The status “Not Confirmed” of the indicator “Location InformationConfirmed in HLR” causes the VLR-F to invoke the MAP_UPDATE_LOCATIONservice after establishment of authenticated radio contact with the MSconcerned.

When the MAP_UPDATE_LOCATION procedure is performed, after receipt ofthe MAP_UPDATE_LOCATION acknowledgement containing the SG number, thestatus of the indicator “Location Information Confirmed in HLR” ischanged to “Confirmed”.

If the MAP_UPDATE_LOCATION procedure is unsuccessful for any reason, thestatus of the indicator “Location Information Confirmed in HLR” remainsunchanged except for the case that the IMSI record in the VLR-F isdeleted because either of the errors “Unknown Subscriber” or “RoamingNot Allowed” has been received from the SG in response to aMAP_UPDATE_LOCATION request.

For “Not Updated” records, if Signal Gateway receives an Update Locationmessage, the MSC and VLR addresses are extracted, stored in the SignalGateway and the record status is changed to “Updated”. A log of recoverymessages attempted and received is generated.

5.5. Compliance

The Signal Gateway of an embodiment complies with the following keyspecifications, but is not so limited: 3GPP TS 09.02 v7.7 R1999/3GPPTS29.002; Q711-716 SCCP; Q761-764 Q767; 3GPP TS 23.003 V3.9.0 (2001June); GSM 03.60 version 6.6.1 Release 1997; GSM 03.90 version 7.0.0Release 1998; GSM 03.40 version 7.4.0 Release 1998/3GPP TS03.40 V7.5.0(2001 December); GSM 03.18 version 6.6.0 Release 1997/3GPP TS 23.018V3.10.0 (2002 January); and OFTA spec 2202/2204.

The Signal Gateway handles the mapping between the MSISDN-H stored inHPMN HLR and the MSISDN-F stored in the Signal Gateway function. Thereare many data services (circuit switch, HSCSD, GPRS) which may notinvolve the MSISDN, and there are SS and USSD services which reach theHPMN real HLR according to the IMSI. In these situations, the SignalGateway function either relays signals to the real destinations at thefirst interaction (where subsequent interactions are directly betweenthe two parties without further participation from the Signal Gateway),or maps them to the real destination by initiating a new transaction andsubsequent iterations pass through the Signal Gateway function.

Table 45 includes the procedures handled by the Signal Gateway of anembodiment.

TABLE 45 Message MAP_Send_Routing_Info_For_SM requestMAP_Send_Routing_Info_For_SM response MAP_Forward_Short_MessageMO-request MAP_Forward_Short_Message MO-responseMAP_Forward_Short_Message MT-request MAP_Forward_Short_MessageMT-response MAP_Report_SM_Delivery_Status requestMAP_Report_SM_Delivery_Status response MAP_Ready_For SM requestMAP_Ready_For_SM response MAP_Alert_Service_Centre requestMAP_Alert_Service_Centre reposnse MAP_Activate_Trace_Mode requestMAP_Activate_Trace_Mode response MAP_Deactivate_Trace_Mode requestMAP_Dectivate_Trace_Mode response MAP_Purge_MS request MAP_Purge_MSresponse MAP_Send_Authentication_Info requestMAP_Send_Authentication_Info response MAP_Delete_Subscriber_Data requestMAP_Delete_Subscriber_Data response MAP_Register_SS requestMAP_Register_SS response MAP_Activate_SS request MAP_Activate_SSresponse MAP_Deactivate_SS request MAP_Deactivate_SS responseMAP_Interrogate_SS request MAP_Interrogate_SS response MAP_Purge_MSrequest MAP_Purge_MS response MAP-Reset request MAP-Restore requestMAP-Restore response MAP-Forward-SS Check indicationMAP-UpdateGPRSLocation MAP-Register-CC entry MAP-Erase-CC entryMAP-processUSSDrequest MAP-UssdRequest MAP-SSInvokeNotify etc

In summary, all MAP messages going through the Signal Gateway are notaffected by the Signal Gateway for the normal services. For ISUPmessages, the Signal Gateway is compliant with OFTA-2202-3 and 2204.

5.6. GPRS

The GPRS service of SIMM subscribers is not affected by the SignalGateway function. Since UpdateGPRSLocation is routed withCdPA=MGT-of-IMSI-H by the SGSN-X, when the message reaches the GMSC-H,GMSC-H's GTT will direct the message to a Signal Gateway. If the SignalGateway function completely fails, the HLR-H that corresponds to the MGTof IMSI-H will be selected as a result of the backup configuration atGMSC-H's GTT configuration.

Assuming a Signal Gateway is chosen by the GMSC-H's GTT, the Signalgateway will not modify the CgPA address but the CdPA to the GT of theHLR-H corresponding to the MGT of IMSI-H without issuing a newtransaction between the Signal Gateway and the HLR-H when the subscriberis not registered at the FPMN. Subsequent interactions are directlybetween HLR-H and SGSN-X. Future transactions initiated by SMSC/HLR suchas SRI-SM or by HLR such as CancelLocation will not involve the SG.

However, if the subscriber registers at the FPMN, the Signal gatewaymodifies the CgPA address to the SG and the CdPA to the GT of the HLR-Hcorresponding to the MGT of IMSI-H by issuing a new transaction betweenthe Signal Gateway and the HLR-H. In particular, the SG becomes the SGSNnumber to HLR-H. The HLR-H interacts with the SG and subsequently withSGSN-F (e.g., insertSubData, acks, etc.) in their correspondingtransaction contexts.

When CancelLocation is issued by HLR-H due to an UpdateGPRSLocation fromanother SGSN, the message is sent directly to the SG which then maps tothe real SGSN-F by issuing a new transaction. When SRI-SM with GPRSsupport indicator issued by a SMSC to HLR-H that also supports GPRS,then the SG will be returned as the SGSN node to the SMSC which thenforwards the message to the SG which forwards the message in turn to thereal SGSN.

In other words, the behavior of GPRS MAP signaling will be very similarto the voice and SMS signaling except that the SGSN plays the role ofVMSC or VLR and hence the Signal Gateway doubles as the SGSN when themobile station registers with GPRS at FPMN.

Table 46 shows the case of updateGPRSLocation by SGSN-F and SRI-SM by aSMSC that supports GPRS. SGSN SSN is 1001-0101 or 95 BCD.

TABLE 46 updateGPRSLoc from SGSN-F to the Message Signal Gateway SignalGateway function via GMSC-H GTT to HLR-H via GMSC-H SCCP Called Address:SCCP Called Address: GT: MGT-H GT: HLR-H SSN:  6 SSN:  6 TT:  0 TT:  0SCCP Calling Address: SCCP Calling Address: GT: SGSN-F GT: SG/SGSN-GTSSN: 95 SSN: 95 TT:  0 TT:  0 MAP level parameters: MAP levelparameters: SGSN: SGSN-F SGSN: SG/unchanged

Note however since SMS will be forwarded to whatever the HPMN-HLR willreturn when it receives a SRI-SM(MSISDN-H), then when SIMM subscriberregisters at a FPMN via SGSN, the Signal Gateway can present accordingto one of the following options: the Signal Gateway presents its HPMN GTto a HPMN HLR for SGSN imitations; the Signal Gateway presents its FPMNGT to a HPMN HLR for SGSN imitations in which case, the FPMN STP isconfigured to translate the FPMN GT in CdPA to the HPMN GT of the SignalGateway; the GT of SGSN-F are passed transparently to HPMN HLR withoutany change (the calling GT of SGSN-F is unchanged when relayed to theHLR-H) (InsertSubData is communicated directly with the SGSN GT and thesignal gateway is bypassed) (recommended).

Table 47 shows the signal translations when the Signal Gateway presentsits HPMN GT to a HPMN HLR for SGSN imitations.

TABLE 47 Message from Signal Gateway Insert Subscriber Data from HLR-Hto SGSN-F via GMSC-H SCCP Called Address: SCCP Called Address: GT: SGGT: SGSN-F SSN: 95 SSN: 95 TT:  0 TT:  0 SCCP Calling Address: SCCPCalling Address: GT: HLR-H GT: SG SSN:  6 SSN:  6 TT:  0 TT:  0 MAPlevel parameters: MAP level parameters: MSISDN: MSISDN-H MSISDN:MSISDN-H

The message is routed to the FPMN SGSN-F. The SCCP Calling Party Addressis replaced with the Signal Gateway GT. This guarantees that when thereply for this message is sent, the GMSC-H can route it to the SignalGateway. Note that unlike UpdateLoc at FPMN, the Signal Gateway does notchange MSISDN-H to MSISDN-F.

FIG. 61 is a signal flow diagram for use of a Signal Gateway (SG) withGeneral Packet Radio Service, under an embodiment.

Note that F-SG is not used to represent the SGSN at the HLR-H when theSignal Gateway is presenting itself to HLR-H for updateGPRSLocation.This is because the SGSN will be returned to the SMSC that supports GPRSin which case SMSC will not be able to route if SGSN is F-SG, andbecause the VLR address is still F-SG which really influences theinsertSubData parameters while roaming.

For GPRS service, there may also be combined IMSI/GPRS attachmentinvolving combined location and routing area update. However since thisinvolves two separate updates from VLR an SGSN to HLR respectively, theSignal Gateway can distinguish when to swap the MSISDN-H by MSISDN-Fwhen the SIMM subscriber is registering in FPMN.

The combined update is achieved by an association created between SGSNand MSC/VLR to provide for interactions between SGSN and MSC/VLR. Theassociation is created when the VLR stores the SGSN number and the SGSNstores the VLR number. The association is used for coordinating MSs thatare both GPRS-attached and IMSI-attached. The association supports thefollowing actions: IMSI attach and detach via SGSN (this makes combinedGPRS/IMSI attach and combined GPRS/IMSI detach possible, thus savingradio resources); coordination of LA update and RA update, includingperiodic updates, thus saving radio resources (a combined RA/LA updateis sent from the MS to the SGSN, and the SGSN forwards the LA update tothe VLR); paging for a CS connection via the SGSN; alert procedures fornon-GPRS services; identification procedures; MM Information procedures.

The SGSN-MSC/VLR association is created at the following occasions:combined IMSI/GPRS attachment; GPRS attachment when the MS is alreadyIMSI-attached; combined RA/LA update when the MS performs IMSIattachment and is already GPRS-attached; and combined RA/LA update whenan IMSI and GPRS-attached MS changes from an area of network operationmode II or III to an area of network operation mode I.

The association between SGSN and MSC/VLR is initiated by the SGSN. TheSGSN creates an association by sending a BSSAP+ message concerning aparticular MS to the VLR. To get the VLR number, the SGSN translates thecurrent RAI to a VLR number via a translation table. During a CSconnection, an MS in class-B mode of operation cannot perform GPRSattach nor routing area updates, only MSs in class-A mode of operationcan perform these procedures. If a GPRS attach was made during a CSconnection, the association shall be initiated by a combined RA/LAupdate after the CS connection has been released.

The association between SGSN and MSC/VLR is updated on the followingoccasions: when an MS changes VLR; and when an MS changes SGSN. Theassociation is not updated during a CS connection.

When the MS is in idle mode (see GSM 03.22), the association betweenSGSN and MSC/VLR is updated with the combined RA/LA updates procedure.

FIG. 62 is another signal flow diagram for use of a Signal Gateway (SG)with General Packet Radio Service, under an embodiment.

Now consider the MT SMS example to MSISDN-H when the subscriber isregistered at SGSN-F. The SMSC-X (SMSC-H, SMSC-F or SMSC-V) issues anSRI-SM MSISDN-H with GPRS support to the HLR-H with GPRS support. TheHLR-H has the address of the Signal Gateway as the SGSN and returns itin SRI-SM response. SMSC-X issues a FSM to the Signal Gateway. TheSignal Gateway performs the translation as shown in Table 48.

TABLE 48 Message from Signal Gateway MT FSM from SMSC-X to SGSN-F viaGMSC-H SCCP Called Address: SCCP Called Address: GT: SG GT: SGSN-F SSN:8 SSN: 8 TT: 0 TT: 0 SCCP Calling Address: SCCP Calling Address: GT:SMSC-X GT: SG SSN: 8 SSN: 8 TT: 0 TT: 0

The Sending SMSC address, the Sender address and the recipient addressin the MAP message are left unchanged. Note that the SCCP CallingAddress has also been changed and hence the response also goes throughthe Signal Gateway as shown in Table 49.

TABLE 49 Message from Signal Gateway MT FSM Response from SGSN-F toSMSC-X via GMSC-H SCCP Called Address: SCCP Called Address: GT: SG GT:SMSC-X SSN: 8 SSN: 8 TT: 0 TT: 0 SCCP Calling Address: SCCP CallingAddress: GT: SGSN-F GT: SG SSN: 8 SSN: 8 TT: 0 TT: 0

FIG. 63 is yet another signal flow diagram for use of a Signal Gateway(SG) with a General Packet Radio Service (GPRS), under an embodiment.The Signal Gateway generates a CDR for this transaction and can be usedto apply special charges/discounts. SGSN-F MT SMS CDR is used for SMSInter-working settlement. Special rates may be negotiated for thespecific HPMN IMSI range for Multiple MSISDN subscriber.

5.7. Send Authentication, USSD and Supplementary MAP Services

All MAP messages on Authentication services, supplementary services andUSSD services are based on IMSI. They can be initiated by MS, e.g., a MOcall can trigger for authentication service. These services areconducted between VMSC and VLR, between VLR and HLR, and between HLR andSCF. Since the Signal Gateway is only a virtual HLR/VLR/GMSC/VMSC, theonly time the Signal Gateway will be involved is between VLR and HLRcommunication.

When the MAP messages on Send-Authentication, supplementary services andUSSD services are routed on MGT between a VLR-X and HLR-H through HPMNwhere X is not a FPMN network, they are redirected to the Signal Gatewayfunction based on GTT on MGT at the GMSC-H. The selected Signal Gatewayrelays the messages to HLR-H that corresponds to the MGT by replacingthe called MGT with the corresponding HLR-H GT without changing thecalling party global title.

Since there is no CgPA change, the transaction initiated by the VLR-Xcan still be retained by the Signal Gateway function without the need toinitiate a new transaction dialog towards the other party. After theinitiating transaction, subsequent interactions within the sametransactional dialog will be directly between HLR and VLR. Therefore,the Signal Gateway function is not involved in the transaction after theinitiating transaction. Thus all services regarding Send-Authentication,SS, USSD can proceed as normal services not affected by the SIMMservice.

However, when the SIMM subscriber is at a FPMN network, the SignalGateway function will become the HLR to the VLR-F. Hence MAPcommunications such as Authentication, supplementary and USSD serviceswill be between VLR-F and SG. So when the SG forwards these services toHLR-H, the SG presents its FPMN SG to the HLR-H so that correspondingHLR procedures might be performed. For example, if a subscriber is notallowed to make changes to call forwarding numbers while roaming, the SGpresents the FPMN SG to HLR. However on the return path back to theVLR-F, SG presents the HPMN GT or more precisely the GT with which theVLR-F initially communicated.

Following is an example using the RegisterSS, with reference to Table50.

TABLE 50 Message from Signal Gateway1 RegisterSS from VLR-F to HLR1 SCCPCalled Address: SCCP Called Address: GT: SG1 GT: HLR1-H SSN: 6 SSN: 6TT: 0 TT: 0 SCCP Calling Address: SCCP Calling Address: GT: VLR-F GT:F-SG1 SSN: 7 SSN: 7 TT: 0 TT: 0

The reason that F-SG1 is introduced is because HPMN HLR procedure couldbe based on the subscriber network location. For example, sometimes callforwarding and call barring services registration may be not allowedwhile roaming. However if HPMN regards the FPMN as an extension of itsnetwork so as not to treat the subscriber as a roamer when registered atthe FPMN, then there is no need to distinguish HPMN SG and FPMN F-SG forthis particular FPMN.

If the HLR procedures can be configured based on VLR GT ranges, thenthere will not be a need to assign two types of GTs (HPMN and FPMN) to aSignal Gateway. The HPMN GTs of the Signal Gateways are simply regardedas roaming GTs by the HLR procedure configuration. As a result, for aSignal Gateway, its FPMN GT will be the same as its HPMN GT. Forexample, to support national roaming, a HLR is configured to indicatewhich address is a roaming GT. The SG GT can be configured like aroaming GT as if it is a roaming GT in national roaming.

Alternatively, if the HPMN network wants to regard a FPMN network as ifit is an extended home network, then there is no need for the FPMN typeof GT for the Signal Gateway function for the FPMN network as shown inTable 51.

TABLE 51 Message from Signal Gateway RegisterSS from HLR-H to VLR-F viaGMSC-H SCCP Called Address: SCCP Called Address: GT: F-SG1 GT: VLR-FSSN: 7 SSN: 7 TT: 0 TT: 0 SCCP Calling Address: SCCP Calling Address:GT: HLR1-H GT: SG1 SSN: 6 SSN: 6 TT: 0 TT: 0

The message is routed to the FPMN VLR. SCCP Calling Party Address isreplaced with the Signal Gateway GT. This guarantees that when the replyfor this message is sent, GMSC-H can route it to the Signal Gateway.

FIG. 64 is a signal flow diagram for use of a Signal Gateway (SG) in thetransfer of Message Application Part (MAP) messages onSend-Authentication, Unstructured Supplementary Service Data (USSD) andsupplementary MAP services, under an embodiment.

The MAP-Process-USSD request is the only one in which the content may bemodified where the optional MSISDN-F parameter in the MAP message fromFPMN is changed to MSISDN-H when the message is going through the SignalGateway as shown in Table 52. This is because MSISDN-H may be used toaddress subscriber data in gsmSCF if the USSD is further sent by HLR togsmSCF for processing.

TABLE 52 ProcesssUSSD from VLR-F to the Signal Message from SignalGateway Gateway function via GMSC-H GTT to HLR-H via GMSC-H SCCP CalledAddress: SCCP Called Address: GT: SG GT: HLR-H SSN: 6 SSN: 6 TT: 0 TT: 0SCCP Calling Address: SCCP Calling Address: GT: VLR-F GT: VLR-F SSN: 7SSN: 7 TT: 0 TT: 0 MAP level parameters: MAP level parameters: IMSI:IMSI-H IMSI: IMSI-H MSISDN: MSISDN-F MSISDN: MSISDN-H

FIG. 65 is another signal flow diagram for use of a Signal Gateway (SG)in the transfer of Message Application Part (MAP) messages onSend-Authentication, Unstructured Supplementary Service Data (USSD) andsupplementary MAP services, under an embodiment.

However, when a network-initiated USSD (e.g. USSDRequest, USSDNotify) issent by the HLR directly towards a Signal Gateway which is treated asthe VLR of the SIMM subscriber when the subscriber registers at FPMN,the Signal Gateway will not only modify the CdPA from the Signal Gatewayto the real VLR-F but also the CgPA to the Signal Gateway in a newtransaction, as shown in Table 53. The response from VLR-F to the SignalGateway will be relayed by the Signal Gateway back to the HLR-H.

TABLE 53 USSDRequest from HLR-H to the Message from Signal GatewaySignal Gateway function to VLR-F SCCP Called Address: SCCP CalledAddress: GT: F-SG GT: VLR-F SSN: 7 SSN: 6 TT: 0 TT: 0 SCCP CallingAddress: SCCP Calling Address: GT: HLR-H GT: SG SSN: 6 SSN: 7 TT: 0 TT:0

FIG. 66 is yet another signal flow diagram for use of a Signal Gateway(SG) in the transfer of Message Application Part (MAP) messages onSend-Authentication, Unstructured Supplementary Service Data (USSD) andsupplementary MAP services, under an embodiment.

5.8. CSD/Fax

Since the IMSI is still a HPMN IMSI and no CSD/Fax related numbers getchanged, these services will be same as a normal subscriber for SIMMsubscribers.

5.9. MMS, IN, Camel and 3G

The MMS, IN, Camel, and 3G services are supported by the Signal Gateway(SG) of an embodiment. Since MMS roaming is based on GPRS roamingdescribed above, MMS roaming service is transparent on top of GPRS.MSISDN-H is not changed at FPMN SGSN so MMSC and GPRS context set upneed not make any modification or permission control on MSISDN-F.

When the SIMM subscriber is sending a MMS to a FPMN country number, themessage goes to the home MMSC first. Unlike SMS messages that aredelivered directly to recipients via home SMSCs, MMS messages areforwarded to the MMSCs of receiving operators in the FPMN (need not bethe FPMN operator). This involves MMS interworking.

Furthermore, when the MMS subscriber of a sending operator in FPMNcountry sends a MMS to MSISDN-F of a SIMM subscriber, since the homeMMSC of MSISDN-F is really MMSC-H, not MMSC-F, when MMSC-F receives theMMS message, it must route them via MMS-internetworking for the specialrange of MSISDN-F numbers.

The MMS-internetworking can be direct bilateral relationships or via MMSbroker/MMS relay. In the former case, HPMN MMSC should arrange to directMMS from SIMM subscribers via the broker/relay.

FIG. 67 is another signal flow diagram for use of a Signal Gateway (SG)with Multimedia Messaging Service, under an embodiment.

When MMS is sent by a SIMM subscriber to a FPMN country number via theMMS broker/relay, the sending MSISDN-H can be changed to MSISDN-F.

When MMS is sent to a SIMM subscriber's MSISDN-F, the MMSC-F isconfigured to route all these message destined to the special ranges ofMSISDN-F via the MMS broker/relay which will then relay the message toMMSC-H after changing the destination address MSISDN-F to MSISDN-H.

5.10. Logging and Reports

The SIMM system of an embodiment includes logging functions in real-timeon SS7 transaction history, roamer history, provisioning transactions,etc. Each can be turned on/off based on configuration options.

The system generates reports including, but not limited to: list ofIMSI, MSISDN-H to MSISDN-F mapping and other subscriber data per FPMNconfigured in system; number of SS7 messages handled with details onindividual message statistics (number of Update Location, InsertSubscriber Data, SRI, SRI-SM etc per FPMN); roamer statistics at FPMNsuch as average number of roamers in FPMN (can be divided down toprovincial networks) at any time, average number of #FTN assigned at anytime, average # of calls made and received through the Signal Gatewayper subscriber, etc.; traffic report such as Call traffic and signalingmessage traffic; current number of MAP transactions and ISUP calls, andtotal number of these transactions in a hour; unsuccessful calls arealso logged with reason of failure (the failure may be due to MAPsignaling (e.g., error message is returned when SRI is sent to HLR) orISUP (e.g. congestion, SIMM subscriber does not answer etc)).

The reports can be conducted daily, weekly and monthly. Customizedreports can be built based on customer requirements.

For generating a monthly report, the daily log files are processedrather than holding the one-month data in the DB. Daily statistics aresaved for use in calculating monthly statistics.

Transactional history data (such as MAP/IUSP transactions, roamerhistory information) is logged in separate disk drive from CDR data toimprove drive-write performance even though both sets of data could bemirrored in each other's drive.

SRI and SRI-SM logs are in both transaction history data and in CDRdata. When they are in CDR data, they use CDR format although adifferent call-type from the other call types (ROAM, FORW, SMS-MT etc).They will also have a separate DB table from other call types CDR.

There is also a configuration option ON/OFF to control whether ISUP/SMSunsuccessful calls are logged or not in the CDR data. However alltransaction data is logged separately in the transaction history data.

Transaction logging based on transaction type (e.g., SendParameters noneed to log, Location update yes, ISUP yes, SRI logging only OR-routed,provisioning transactions, maintenance transactions etc) can also beturned on/off based on switch options.

5.11. OAMP (Operation, Administration, Maintenance and Provisioning),Access Control and Overloading

The SIMM system of an embodiment supports a provisioning interface(including browser and HTTP API, text file, XML file, stored proceduresfor DB, etc.) where the administrator can configure Systemconfiguration, Global Titles, Participating PMN based configuration,different pools of #s, OR-allow tables, etc. Mapping between MSISDN-Hand MSISDN-F is also maintained using this interface. It is alsopossible to define network capabilities and specify the various FPMNthat are participating in this service deployment. If the subscriberopts-out of the service, they should surrender their SIM cards eventhough they will be able to keep the same HPMN MSISDN (where numberportability applies). The FPMN MSISDN will be quarantined.

The Signal Gateway provides a web interface for use by administrators indefining user groups and their associated rights on different operatorsof the Signal Gateway configurations. Only administrators are alloweddirect access to the Signal Gateway function via a Unix system console.

The Signal Gateway publishes SNMP v1 traps in case of critical failuresor warnings. The MIB also supports set and get SNMP methods to retrieveand set run-time information. System can be shutdown remotely, ifrequired.

Components of the SIMM System monitor the critical processes of thesystem. If any process fails, the process is automatically restarted orthe system switchovers to another node (if it is running inactive-standby mode). Each node is dimensioned to support the totalload. In case of switchover, the new node can take over the total load.There is a means to display the active-standby status of the systemcomponents.

Also, SIMM System displays the status of different physical interfaces.The interfaces cover the system signaling links for sending andreceiving SS7 message, the ISUP loopback signaling and the externaldatabase. In case of major breakdown of these interfaces, alerts can begenerated to a maintenance staff. If any in-service signaling links aredown, there is a minor alarm. If all of them are down, there is aCritical alarm. The signaling links carry both MAP and ISUP messages. Ifthe database connection fails (e.g., due to LAN failure, databaseshutdown, etc.), the system re-establishes the database connection whenthe database is up and generates an alarm to indicate DB connection isdown.

The SIMM System also supports other performance and capacity relatedindications such as those relating to the CPU, memory, MAP transactionrate, BHCA and SS7 loading, etc.

Any call duration longer than a configurable timer, (e.g., 1 hour) willbe specially handled. It can be continued with an alarm flag or releaseddepending on a control flag.

The Signal Gateway function also tracks the transaction loading of thesystem. Alarms are generated when memory, CPU, and transaction ratesexceed pre-specified thresholds. In this case, the Signal Gateway canchoose to reject certain type of SS7 messages, e.g., SMS, so that thesending SMSC can queue it at its end. The Signal Gateway can also rejectmessages based on FPMN. The Signal Gateway can also choose to relay fornew LUP messages so the SIMM subscribers can be handled as normalroamers as if the Signal Gateway function fails; this relay can beapplied based on FPMN during times of system overloading.

5.12. Call Detail Record

As described above, CDRs are generated for ISUP calls, SMSs and theirassociated MAP transactions. The CDRs are stored in the database aftereach call. For calls of long duration, periodic updates of the CDR inthe DB also take place. Duplicated and missing CDRs are safe-guarded bya sequence number. Long records share the same sequence number but useadditional intermediate sequence numbers to relate them.

CDR records are converted to files of any switch format based on theASN.1 format of the switch CDR. Transmission of CDR files to externalsystems can be physically delivered or via FTP.

A separate billing related document is prepared in the CDR customizationprocess. Key information elements captured in the call detail record areshown in Table 54, but the embodiment is not so limited.

TABLE 54 S. No Information Element 1. Call Type 2. Signal Gateway ID 3.Start Date [DD MM YY] 4. Start Time [HH MM SS] 5. Call Setup Duration[HH MM SS] 6. Effective Call Duration [HH MM SS] 7. Incoming Group/TrunkID 8. Outgoing group/Trunk ID 9. Calling Party Details 10. Called PartyDetails 11. Backward Call Indicator 12. Forward Call Indicator 13. CallReference 14. Additional Called Party Details 15. Call End Reason 16.IMSI 17. MSISDN-F 18. MSISDN-H 19. Originating SRI-issuing MSC 20.Terminating VLR 21. MSRN 22. #MSRN 23. FTN 24. #FTN 25. Original calledparty number 26. Original calling party number 27. SMSC 28. Messagelength 29. Terminating VMSC 30. Call Forwarding Reason 31. IntermediateSequence # 32. Sequence number Delivery time etc

The call type will indicate different CDR type, such as Roaming call,forwarding call, SRI, SRI-SM. Only MTC (call or SMS including callforwarding, call transfer, call re-routing due to roaming) types ofrecords are generated. MO records (call or SMS), SUPS (supplementaryservices) and USSD service records are not the responsibilities of theSignal Gateway function.

The original called party number indicates whether MSISDN-F or MSISDN-Hwas originally called or SMSed. The originating SRI-issuing MSCindicates which network GMSC issued the SRI query so to determine wherethe call originates from FPMN or HPMN. The additional called partydetails are those captured in the IAM messages. The forwardingindicators might contain charge indicators.

The FTN and Call Forwarding Reason fields indicate whether callforwarding/transfer has taken place or not and whether it isearly/unconditional/transfer call forwarding or late call forwarding.The SRI event can be configured to log only cases where optimal routinghas been applied.

All MAP transactions and ISUP transactions can also be logged. Allcall/SMS records can also be generated for unsuccessful cases as well assuccessful ones depending on configuration options.

The CDR is customized based on HPMN mediation system requirements. TheSignal Gateway CDRs can be mapped to the different call types (e.g.,FORW for forwarding, ROAM for roaming, MO, transit, MO-SMS, LOCA forlocation update, HLRI for locating subscriber, etc.) of the HPMN CDRtypes. Other HPMN CDR specific parameters (e.g., tariff class, chargingzone, charging type, call type, etc.) can also be deduced from theSignal Gateway CDRs.

5.12.1. IMSI/MSISDN-H/F Not Found in DB

A Location Update/processUSSD request/SS related message (routed by MGT)can be received by the SG, wherein the IMSI data is not present in theDB. This can happen when the subscriber de-subscribes the SIMM servicebut fails to replace the SIM card. In this situation there will be aconfiguration option for HPMN to select one of the two followingactions: SG rejects the request; and SG passes the message to the HLR bymodifying the SCCP called party address to HLR and keeping the VLR-F asthe SCCP calling party address (there is a table which maps the IMSIrange to the corresponding HLR; if the IMSI does not match it can map toa default HLR). An error log is generated under either option.

If the entire SG function goes down, a SIMM user location Update in FPMNhas direct communication between the VMSC-F and HLR-H. After the SG isrestored, the ProcessUSSDRequest is routed to the SG. The MSISDN fieldis an optional field. If it is present, it contains MSISDN-H. In thiscase, SG modifies the SCCP called party address to HLR and keeps theVLR-F as the SCCP calling party address.

6. Hardware and Software Components

Various components can be used to provide the services described herein.The components include, for example, an Application Server, Database,SS7 cards, etc, but are not so limited.

Table 55 shows example specifications for hardware components used tohost and run the SIMM Service for two FPMN operators and a totalregistered subscriber count of 50,000 assuming 30% of them are roamingat an FPMN at any point in time (15,000 simultaneous roaming subscribersof SIMM Service at FPMN), under an embodiment. The ASN.1 is fromObjective Systems. Host-based protocol stacks include SCCP, ISUP etc.

TABLE 55 S. No Description Qty Comments 1. Sun Netra V480 with AC power4 2 app servers + 2 DB servers 4 CPU each of 900 MHz 4 GB RAM 72 GB Diskspace (2 Disks of 36 GB Mirrored) For DB server 144 GB Disk space(mirrored) and 8 G RAM 6 PCI slots Dual Ethernet NIC 19″ rack mount kitTape Drive CD-ROM Drive Two 100-240 VAC power supplies 2. Data kinetics(Intel) Quad E1 PCI SS7 4 Each card has 4 E1 links board 2 card per appserver 3. Board based SS7 protocol stacks 4 (MTP1, MTP2 and MTP3) 4.Host based SS7 protocol stack ISUP, 2 1 per host app server SCCP CL(SCCP Connectionless) for Septel cards on Solaris 8 5. Objective SystemsASN.1 run-time 2 license 6. Oracle 8.1.7 Enterprise Edition with 1 Use10 per processor. Have two fail-safe, TAF and replication supportsystems with 4 CPU; hence 80 for 40 “Named User” license named userlicense

Table 56 shows example specifications for hardware components used tohost and run the SIMM Service for two FPMN operators and a totalregistered subscriber count of 20,000 assuming, under an embodiment.

TABLE 56 S. No Description Qty Comments 1. Sun Fire V-480 with AC power4 2 app servers and 2 DB servers 2 CPU each of 900 MHz 2 GB RAM 2 * 36GB Disk space (2 Disks of 36 GB Mirrored) For DB server use 4 G RAM and4X36 GM DB server 6 PCI slots Dual Ethernet NIC 19″ rack mount kit TapeDrive CD-ROM Drive Two 100-240 VAC power supplies 2. Data kinetics(Intel) Quad E1 PCI SS7 2 Each card has 4 E1 links board 3. Board basedSS7 protocol stacks 2 (MTP1, MTP2 and MTP3) 4. Host based SS7 protocolstack ISUP, 2 SCCP CL (SCCP Connectionless) for Septel cards on Solaris8 5. Objective Systems ASN.1 run-time 2 license 6. Oracle 8.1.7Enterprise Edition with 1 Use 10 per processor. Have two fail-safe, TAFand replication support systems with 2 CPU; hence 40 for 40 “Named User”license named user license

A SIMM System and method is provided that supports many MobileSubscriber Integrated Service Digital Network (MSISDN) numbers on amobile device. The SIMM System and Service is also referred to as SingleIMSI Multiple MSISDN Service (SIMM). The system of an embodimentcomprises: a mobile device including a Subscriber Identity Module (SIM)and an International Mobile Subscriber Identity (IMSI); a first MobileSubscriber Integrated Service Digital Network (MSISDN) number for use ina first public mobile network; a second MSISDN number for use in asecond public mobile network; and at least one signal gateway coupledamong components of the first public mobile network and the secondpublic mobile network, wherein the signal gateway couples calls betweenthe SIM and the first public mobile network using the first MSISDN,wherein the signal gateway couples calls between the SIM and the secondpublic mobile network using the second MSISDN.

At least one of the first MSISDN number and the second MSISDN number ispermanently assigned to the SIM in the system of an embodiment.

At least one of the first MSISDN number and the second MSISDN number istemporarily assigned to the SIM in the system of an embodiment.

The first MSISDN number of an embodiment is a telephone number of themobile device that is local to the first public mobile network.

The second MSISDN number of an embodiment is a telephone number of themobile device that is local to the second public mobile network.

Components of the signal gateway of an embodiment map the first MSISDNnumber to the second MSISDN number.

The system of an embodiment includes at least one component of thesignal gateway that provides at least one of a home location register(HLR), a visited location register (VLR), a gateway mobile switchingcenter (GMSC), a visited mobile switching center (VMSC), a short messageservice center (SMSC), and a service node in at least one of the firstpublic mobile network and the second public mobile network.

In the system of an embodiment the signal gateway is coupled to at leastone first mobile switching center of the first public mobile network andis coupled to provide signal loop-back at the first mobile switchingcenter, wherein the signal gateway couples to at least one component ofthe second public mobile network via the first mobile switching center.

The signal gateway of an embodiment is coupled to at least one secondmobile switching center of the second public mobile network and iscoupled to provide signal loop-back at the second mobile switchingcenter, wherein the signal gateway couples to at least one component ofthe first public mobile network via the second mobile switching center.

The first public mobile network of an embodiment includes first andsecond mobile switching centers, wherein the at least one signal gatewayincludes first and second signal gateways coupled among the first andsecond mobile switching centers via couplings that support SignalingSystem Number 7 (SS7) protocols.

The first signal gateway of an embodiment couples to the first mobileswitching center using a common signal point code. The first signalgateway also couples to the second mobile switching center using a firstsignal point code. The second signal gateway of an embodiment couples tothe first mobile switching center using a second signal point code.Further, the second signal gateway couples to the second mobileswitching center using the common signal point code.

The first signal gateway of another embodiment couples to the firstmobile switching center using a first signal point code. The secondsignal gateway couples to the second mobile switching center using asecond signal point code.

The second public mobile network of an embodiment includes third andfourth mobile switching centers, wherein the at least one signal gatewayincludes third and fourth signal gateways coupled among the third andfourth mobile switching centers via couplings that support SignalingSystem Number 7 (SS7) protocols.

The third signal gateway of the second public mobile network of anembodiment couples to the third mobile switching center using a commonsignal point code. The third signal gateway also couples to the fourthmobile switching center using a first signal point code. The fourthsignal gateway couples to the third mobile switching center using asecond signal point code; the fourth signal gateway also couples to thefourth mobile switching center using the common signal point code.

In the second public mobile network of another embodiment the thirdsignal gateway couples to the third mobile switching center using afirst signal point code and the fourth signal gateway couples to thefourth mobile switching center using a second signal point code.

The mobile device of the system of an embodiment includes at least oneof cellular telephones, personal computers, portable computing devices,portable telephones, portable communication devices, subscriber devicesor units, and personal digital assistants.

The SIMM System/Service of an embodiment comprises at least one of meansfor wireless communications, means for associating a single subscriberidentity with the means for wireless communications, and means forcoupling calls among the means for wireless communications and a firstpublic mobile network using a first telephone number and for couplingcalls among the means for wireless communications and a second publicnetwork using a second telephone number.

The system of an embodiment includes a wireless client device thatincludes one Subscriber Identity Module (SIM) having one assignedInternational Mobile Subscriber Identity (IMSI), and at least one signalgateway that supports use of two or more Mobile Subscriber IntegratedService Digital Network (MSISDN) numbers by the client device, whereinthe signal gateway couples among at least one of first and second mobileswitching centers, wherein the signal gateway couples calls between theclient device and the first mobile switching center using a first MSISDNand couples calls between the client device and a second mobileswitching center using a second MSISDN.

The SIMM System/Service of an embodiment includes a device comprising atleast one signal gateway coupled among components of a first publicmobile network and a second public mobile network, wherein the signalgateway couples calls between a mobile device and the first publicmobile network using a first Mobile Subscriber Integrated ServiceDigital Network (MSISDN) number, wherein the signal gateway couplescalls between the SIM and the second public mobile network using asecond MSISDN, wherein the mobile device includes a single SubscriberIdentity Module (SIM) and International Mobile Subscriber Identity(IMSI).

The first MSISDN number of the device of an embodiment is a telephonenumber of the mobile device that is local to the first public mobilenetwork and the second MSISDN number is a telephone number of the mobiledevice that is local to the second public mobile network.

The signal gateway of an embodiment maps the first MSISDN number to thesecond MSISDN number.

The signal gateway of an embodiment provides at least one of a homelocation register (HLR), a visited location register (VLR), a gatewaymobile switching center (GMSC), a visited mobile switching center(VMSC), a short message service center (SMSC), and a service node in atleast one of the first and second public mobile networks.

The signal gateway of an embodiment is coupled to at least one firstmobile switching center of the first public mobile network and iscoupled to provide signal loop-back at the first mobile switchingcenter, wherein the signal gateway couples to at least one component ofthe second public mobile network via the first mobile switching center.

The signal gateway of an embodiment is coupled to at least one secondmobile switching center of the second public mobile network and iscoupled to provide signal loop-back at the second mobile switchingcenter, wherein the signal gateway couples to at least one component ofthe first public mobile network via the second mobile switching center.

The first public mobile network of an embodiment includes first andsecond mobile switching centers, wherein the at least one signal gatewayincludes first and second signal gateways coupled among the first andsecond mobile switching centers via couplings that support SignalingSystem Number 7 (SS7) protocols. An embodiment includescross-connections between the first and second signal gateways and thefirst and second mobile switching centers.

The second public mobile network of an embodiment includes third andfourth mobile switching centers, wherein the at least one signal gatewayincludes third and fourth signal gateways coupled among the third andfourth mobile switching centers via couplings that support SignalingSystem Number 7 (SS7) protocols. An embodiment includescross-connections between the third and fourth signal gateways and thethird and fourth mobile switching centers.

The mobile device of an embodiment includes at least one of cellulartelephones, personal computers, portable computing devices, portabletelephones, portable communication devices, subscriber devices or units,and personal digital assistants.

The SIMM System/Service described herein includes at least one methodfor supporting multiple Mobile Subscriber Integrated Service DigitalNetwork (MSISDN) numbers in a mobile device, comprising at least one of:connecting calls between the mobile device and a first public mobilenetwork using a first MSISDN that is associated with the first publicmobile network, wherein the mobile device includes a Subscriber IdentityModule (SIM) with an International Mobile Subscriber Identity (IMSI);mapping the first MSISDN number to a second MSISDN number that isassociated with a second public mobile network; and connecting callsbetween the client device and the second public mobile network using thesecond MSISDN via a coupling through the first public mobile network.

The IMSI of an embodiment is associated with the first public mobilenetwork.

Connecting calls between the mobile device and the first public mobilenetwork in an embodiment comprises coupling calls between the firstpublic mobile network and the SIM via at least one signal gateway,wherein the signal gateway is coupled among components of the firstpublic mobile network and the second public mobile network.

The first MSISDN number of an embodiment is a telephone number of themobile device that is local to the first public mobile network and thesecond MSISDN number is a telephone number of the mobile device that islocal to the second public mobile network.

Components of a signal gateway of an embodiment coupled to at least oneof the first and second public mobile networks map the first MSISDNnumber to the second MSISDN number.

Connecting calls in an embodiment between the mobile device and each ofthe first and second public mobile networks includes coupling the firstand second public networks using at least one signal gateway, wherein atleast one component of the signal gateway provides at least one of ahome location register (HLR), a visited location register (VLR), agateway mobile switching center (GMSC), a visited mobile switchingcenter (VMSC), a short message service center (SMSC), and a service nodein at least one of the first public mobile network and the second publicmobile network.

Connecting calls in an embodiment between the mobile device and each ofthe first and second public mobile networks includes coupling at leastone signal gateway to at least one first mobile switching center of thefirst public mobile network to provide signal loop-back at the firstmobile switching center, wherein the signal gateway couples to at leastone component of the second public mobile network via the first mobileswitching center.

Connecting calls in an embodiment between the mobile device and each ofthe first and second public mobile networks includes coupling at leastone signal gateway to at least one second mobile switching center of thesecond public mobile network to provide signal loop-back at the secondmobile switching center, wherein the signal gateway couples to at leastone component of the first public mobile network via the second mobileswitching center.

The mobile devices of the methods of an embodiment include at least oneof cellular telephones, personal computers, portable computing devices,portable telephones, portable communication devices, subscriber devicesor units, and personal digital assistants.

A computer readable medium is provided herein that includes executableinstructions which, when executed, provide numerous Mobile SubscriberIntegrated Service Digital Network (MSISDN) numbers in a mobile device,by: connecting calls between the mobile device and a first public mobilenetwork using a first MSISDN that is associated with the first publicmobile network, wherein the mobile device includes a Subscriber IdentityModule (SIM) with an International Mobile Subscriber Identity (IMSI);mapping the first MSISDN number to a second MSISDN number that isassociated with a second public mobile network; and connecting callsbetween the client device and the second public mobile network using thesecond MSISDN via a coupling through the first public mobile network.

Aspects of the SIMM system/service described herein may be implementedas functionality programmed into any of a variety of circuitry,including programmable logic devices (PLDs), such as field programmablegate arrays (FPGAs), programmable array logic (PAL) devices,electrically programmable logic and memory devices and standardcell-based devices, as well as application specific integrated circuits(ASICs). Some other possibilities for implementing aspects of the SIMMsystem/service include: microcontrollers with memory (such aselectronically erasable programmable read only memory (EEPROM)),embedded microprocessors, firmware, software, etc. Furthermore, aspectsof the SIMM system/service may be embodied in microprocessors havingsoftware-based circuit emulation, discrete logic (sequential andcombinatorial), custom devices, fuzzy (neural) logic, quantum devices,and hybrids of any of the above device types. Of course the underlyingdevice technologies may be provided in a variety of component types,e.g., metal-oxide semiconductor field-effect transistor (MOSFET)technologies like complementary metal-oxide semiconductor (CMOS),bipolar technologies like emitter-coupled logic (ECL), polymertechnologies (e.g., silicon-conjugated polymer and metal-conjugatedpolymer-metal structures), mixed analog and digital, etc.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense as opposed to anexclusive or exhaustive sense; that is to say, in a sense of “including,but not limited to.” Words using the singular or plural number alsoinclude the plural or singular number respectively. Additionally, thewords “herein,” “hereunder,” “above,” “below,” and words of similarimport, when used in this application, refer to this application as awhole and not to any particular portions of this application. When theword “or” is used in reference to a list of two or more items, that wordcovers all of the following interpretations of the word: any of theitems in the list, all of the items in the list and any combination ofthe items in the list.

The above description of illustrated embodiments of the SIMMsystem/service is not intended to be exhaustive or to limit the systemto the precise form disclosed. While specific embodiments of, andexamples for, the SIMM system/service are described herein forillustrative purposes, various equivalent modifications are possiblewithin the scope of the SIMM system/service, as those skilled in therelevant art will recognize. The teachings of the SIMM system/serviceprovided herein can be applied to other processing systems andcommunication systems, not only for the SIMM system/service describedabove.

The elements and acts of the various embodiments described above can becombined to provide further embodiments. These and other changes can bemade to the SIMM system/service in light of the above detaileddescription.

All of the above references and United States patents and patentapplications are incorporated herein by reference. Aspects of the SIMMsystem/service can be modified, if necessary, to employ the systems,functions and concepts of the various patents and applications describedabove to provide yet further embodiments of the SIMM system/service.

In general, in the following claims, the terms used should not beconstrued to limit the SIMM system/service to the specific embodimentsdisclosed in the specification and the claims, but should be construedto include all processing and communication systems that operate underthe claims to provide the SIMM system/service. Accordingly, the SIMMsystem/service is not limited by the disclosure, but instead the scopeof the system is to be determined entirely by the claims.

While certain aspects of the SIMM system/service are presented below incertain claim forms, the inventor contemplates the various aspects ofthe system in any number of claim forms. For example, while only oneaspect of the system is recited as embodied in computer-readable medium,other aspects may likewise be embodied in computer-readable medium.Accordingly, the inventor reserves the right to add additional claimsafter filing the application to pursue such additional claim forms forother aspects of the SIMM system/service.

1. A communication system comprising: a mobile device of a first publicmobile network, the mobile device including a Subscriber Identity Module(SIM), the SIM having a single International Mobile Subscriber Identityin the first public mobile network (IMSI-H), wherein the first publicmobile network has a Home Location Register (HLR) including a single HLRprofile corresponding to the IMSI-H; a first Mobile SubscriberIntegrated Service Digital Network (MSISDN) number for use in the firstpublic mobile network, the first MSISDN corresponding to the single HLRprofile; a second MSISDN number for use in a second public mobilenetwork belonging to a network operator different from that of the firstpublic mobile network, the second MSISDN corresponding to the single HLRprofile; and at least one signal gateway routing a first communicationbetween the mobile device and the first public mobile network using thefirst MSISDN, and routing a second communication between the mobiledevice and the second public mobile network using the second MSISDN,wherein the at least one signal gateway routes the first and secondcommunications using the single IMSI-H, and wherein the first publicmobile network and the second public mobile network have a roamingagreement.
 2. The system of claim 1, wherein at least one of the firstMSISDN number and the second MSISDN number is permanently assigned tothe SIM.
 3. The system of claim 1, wherein at least one of the firstMSISDN number and the second MSISDN number is temporarily assigned tothe SIM.
 4. The system of claim 1, wherein the at least one signalgateway is coupled to at least one first mobile switching center of thefirst public mobile network and is coupled to provide signal loop-backat the first mobile switching center, wherein the at least one signalgateway couples to at least one component of the second public mobilenetwork via the first mobile switching center.
 5. The system of claim 1,wherein the second public mobile network includes third and fourthmobile switching centers, wherein the at least one signal gatewayincludes third and fourth signal gateways coupled among the third andfourth mobile switching centers via couplings that support SignalingSystem Number 7 (SS7) protocols.
 6. The system of claim 1, wherein themobile device includes at least one of cellular telephones, personalcomputers, portable computing devices, portable telephones, portablecommunication devices, subscriber devices or units, and personal digitalassistants.
 7. The communication system of claim 1, wherein the firstpublic mobile network is a Home Public Mobile Network (HPMN) and thesecond public mobile network is a Foreign Public Mobile Network (FPMN).8. A communication system comprising: means for wireless communications;means for associating a single subscriber identity with the means forwireless communications; and means for routing communication among themeans for wireless communications and a first public mobile networkusing a first telephone number and for routing communication among themeans for wireless communications and a second public mobile networkusing a second telephone number, wherein the communication is routedusing a single subscriber identity; wherein the single subscriberidentity comprises a single International Mobile Subscriber Identity inthe first public mobile network (IMSI-H), wherein the first publicmobile network has a Home Location Register (HLR) including a single HLRprofile corresponding to the IMSI-H, wherein the first telephone numberand the second telephone number correspond to the single HLR profile,wherein the second public mobile network belongs to a network operatordifferent from that of the first public mobile network, and wherein thefirst public mobile network and the second public mobile network have aroaming agreement.
 9. A system comprising a wireless client device thatincludes: one Subscriber Identity Module (SIM) having one assignedInternational Mobile Subscriber Identity in a first public mobilenetwork (IMSI-H), and at least one signal gateway that supports use oftwo or more Mobile Subscriber Integrated Service Digital Network(MSISDN) numbers by the client device, wherein the at least one signalgateway couples among at least one of first and second mobile switchingcenters that correspond to the first public mobile network and a secondpublic mobile network, respectively, wherein the at least one signalgateway routes communication between the client device and the firstmobile switching center using a first MSISDN and routes communicationbetween the client device and a second mobile switching center using asecond MSISDN, wherein the communication is routed using the one IMSI-H,wherein the first public mobile network has a Home Location Register(HLR) including a single HLR profile corresponding to the IMSI-H,wherein the two or more MSISDN numbers correspond to the single HLRprofile, wherein the second public mobile network belongs to a networkoperator different from that of the first public mobile network, andwherein the first public mobile network and the second public mobilenetwork have a roaming agreement.
 10. A device comprising: at least onesignal gateway coupled among components of a first public mobile networkand a second public mobile network, wherein the at least one signalgateway routes communication between a mobile device and the firstpublic mobile network using a first Mobile Subscriber Integrated ServiceDigital Network (MSISDN) number, wherein the at least one signal gatewayroutes communication between the mobile device and the second publicmobile network using a second MSISDN, wherein the mobile device includesa single Subscriber Identity Module (SIM) and a single InternationalMobile Subscriber Identity in the first public mobile network (IMSI-H),wherein the first public mobile network has a Home Location Register(HLR) including a single HLR profile corresponding to the IMSI-H,wherein the first MSISDN and the second MSISDN correspond to the singleHLR profile, wherein the second public mobile network belongs to anetwork operator different from that of the first public mobile network,and wherein the first public mobile network and the second public mobilenetwork have a roaming agreement.
 11. The device of claim 10, whereinthe first MSISDN number is a telephone number of the mobile device thatis local to the first public mobile network and the second MSISDN numberis a telephone number of the mobile device that is local to the secondpublic mobile network.
 12. The device of claim 10, wherein the at leastone signal gateway maps the first MSISDN number to the second MSISDNnumber.
 13. A method for supporting multiple Mobile SubscriberIntegrated Service Digital Network (MSISDN) numbers in a mobile device,comprising: routing communication between the mobile device and a firstpublic mobile network using a first MSISDN that is associated with thefirst public mobile network, wherein the mobile device includes aSubscriber Identity Module (SIM) with a single International MobileSubscriber Identity in the first public mobile network (IMSI-H); mappingthe first MSISDN number to a second MSISDN number that is associatedwith a second public mobile network; and routing communication betweenthe client device and the second public mobile network using the secondMSISDN via a coupling through the first public mobile network using thesingle IMSI-H, wherein the first public mobile network has a HomeLocation Register (HLR) including a single HLR profile corresponding tothe IMSI-H, wherein the first MSISDN and the second MSISDN correspond tothe single HLR profile, wherein the second public mobile network belongsto a network operator different from that of the first public mobilenetwork, and wherein the first public mobile network and the secondpublic mobile network have a roaming agreement.
 14. The method of claim13, wherein the IMSI is associated with the first public mobile network.15. The method of claim 13, wherein routing communication between themobile device and the first public mobile network comprises routingcommunication between the first public mobile network and the SIM via atleast one signal gateway, wherein the signal gateway is coupled amongcomponents of the first public mobile network and the second publicmobile network.
 16. A computer program readable storage medium includingexecutable instructions encoded therein, which, when executed, providenumerous Mobile Subscriber Integrated Service Digital Network (MSISDN)numbers in a mobile device, by: routing communication between the mobiledevice and a first public mobile network using a first MSISDN that isassociated with the first public mobile network, wherein the mobiledevice includes a Subscriber Identity Module (SIM) with a singleInternational Mobile Subscriber Identity in the first public mobilenetwork (IMSI-H); mapping the first MSISDN number to a second MSISDNnumber that is associated with a second public mobile network; andconnecting calls between the client device and the second public mobilenetwork using the second MSISDN via a coupling through the first publicmobile network using the single IMSI-H; wherein the first public mobilenetwork has a Home Location Register (HLR) including a single HLRprofile corresponding to the IMSI-H, wherein the first MSISDN and thesecond MSISDN correspond to the single HLR profile, wherein the secondpublic mobile network belongs to a network operator different from thatof the first public mobile network, and wherein the first public mobilenetwork and the second public mobile network have a roaming agreement.17. A communication system comprising: a mobile device including aSubscriber Identity Module (SIM) and a single International MobileSubscriber Identity in a first public mobile network (IMSI-H); a firstMobile Subscriber Integrated Service Digital Network (MSISDN) number foruse in the first public mobile network; a plurality of second MSISDNnumbers for use in at least one second public mobile network; and atleast one signal gateway coupled among components of the first publicmobile network and the second public mobile network, wherein the atleast one signal gateway routes communication between the SIM and thefirst public mobile network using the first MSISDN, wherein the at leastone signal gateway automatically routes communication between the SIMand the second public mobile network using one of the plurality ofsecond MSISDNs using the single IMSI-H, wherein the first public mobilenetwork has a Home Location Register (HLR) including a single HLRprofile corresponding to the IMSI-H, wherein the first MSISDN and theplurality of second MSISDNs correspond to the single HLR profile,wherein the second public mobile network belongs to a network operatordifferent from that of the first public mobile network, and wherein thefirst public mobile network and the second public mobile network have aroaming agreement.
 18. The system of claim 17, wherein at least one ofthe first MSISDN number and one of the plurality of second MSISDNnumbers is permanently assigned to the SIM.
 19. A method for supportingmultiple Mobile Subscriber Integrated Service Digital Network (MSISDN)numbers in a mobile device, comprising: routing communication betweenthe mobile device and a first public mobile network using a first MSISDNnumber that is associated with the first public mobile network, whereinthe mobile device includes a Subscriber Identity Module (SIM) withsingle International Mobile Subscriber Identity in the first publicmobile network (IMSI-H); mapping the first MSISDN number to one of aplurality of second MSISDN numbers that are associated with a secondpublic mobile network; and automatically routing communication betweenthe client device and the second public mobile network using one of theplurality of second MSISDN numbers via a coupling through the firstpublic mobile network using the single IMSI-H; wherein the first publicmobile network has a Home Location Register (HLR) including a single HLRprofile corresponding to the IMSI-H, wherein the first MSISDN and theplurality of second MSISDNs correspond to the single HLR profile,wherein the second public mobile network belongs to a network operatordifferent from that of the first public mobile network, and wherein thefirst public mobile network and the second public mobile network have aroaming agreement.
 20. A method for routing communication, the methodcomprising: assigning a first Mobile Subscriber Integrated ServiceDigital Network (MSISDN) number to a mobile device for use in a firstpublic mobile network, the mobile device having a Subscriber IdentityModule (SIM) and a single International Mobile Subscriber Identity inthe first public mobile network (IMSI-H), wherein the first publicmobile network has a Home Location Register (HLR) including a single HLRprofile corresponding to the IMSI-H; assigning a second MSISDN number tothe mobile device for use in a second public mobile network; andoptimally routing communication between the SIM and the second publicmobile network using the second MSISDN and the single IMSI-H via asignal gateway, wherein the signal gateway is coupled among componentsof the first public mobile network and the second public mobile network;wherein the first MSISDN number and the second MSISDN number correspondto the single HLR profile, wherein the first MSISDN number is atelephone number of the mobile device that is local to the first publicmobile network, wherein the second MSISDN number is a telephone numberof the mobile device that is local to the second public mobile network,wherein the mobile device is roaming in the second public mobilenetwork, wherein the second public mobile network belongs to a networkoperator different from that of the first public mobile network, andwherein the first public mobile network and the second public mobilenetwork have a roaming agreement.